JP6038279B2 - Method for eluting gold and silver and method for recovering gold and silver using the same - Google Patents

Description

  The present invention relates to a gold and silver elution method and a gold and silver recovery method using the same.

  Gold and silver are highly valuable metals, exist as simple particles in natural veins, and are contained in pyrite, chalcopyrite, and other sulfide metal ores as traces. The recovery method is disclosed in, for example, Patent Document 1 and is examined by a dry method and a wet method, respectively. In the case of a wet method, gold or silver is dissolved in a liquid by leaching and then adsorbed on activated carbon. When recovering gold and silver from the recovered activated carbon, a method of recovering by burning the activated carbon or a method of recovering by eluting gold into a solution is performed.

  In addition, as a method of preferentially eluting gold from activated carbon that adsorbs both gold and silver in a cyanide solution containing both gold and silver, there is known a method of eluting with a solution in which sodium sulfide is mixed with an aqueous caustic soda solution. (Patent Document 2).

  Gold is often contained as a by-product in pyrite, chalcopyrite, and other sulfide metal ores, not gold veins, and gold is separated when smelting its main component and separately smelted into metal gold There are many.

  In the case of gold contained in the metal sulfide ore as a by-product, such as chalcopyrite, generally, the gold is transferred to the anode in the dry copper smelting process, and then concentrated in the electrolytic slime in the electrolytic purification process. Gold in the electrolytic slime is recovered as metallic gold by a wet smelting method (Patent Documents 3 and 4) or a dry smelting method.

  In recent years, considering the environmental impact and impurities in concentrates, smelting technology that treats concentrates by a wet method without using a dry method has been studied, and it has a strong oxidation potential sufficient to dissolve precious metals. A method of leaching gold with a simple acid has been proposed (Patent Document 5). In the method described in Patent Document 5, when an acid halide solution is used to leach gold, the halide forms a stable complex with a noble metal such as gold, but it may be a weaker ligand than cyanide. Is shown (paragraph 0017 in the specification of Patent Document 5). In addition, it has been shown that a solution containing a noble metal can be recovered by adsorbing it on activated carbon, and further shows a method of recovering the noble metal by electrowinning the activated carbon by burning the activated carbon or eluting it with a cyanide solution. (Paragraph 0019 in the specification of Patent Document 5). Further, as a gold adsorbent, an adsorbent using a lignin derivative as a raw material is also known (Patent Document 6).

JP-A-6-145828 US Pat. No. 2,579,531 JP-A-9-316561 JP 2001-316735 A JP 2006-512484 A JP 2005-305329 A

  For elution of gold and silver in activated carbon, it is known that when a cyan solution is used as an eluent, both the elution rate and the recovery rate are improved. However, since the cyan solution is toxic, there are many restrictions on the method of use. Therefore, it is desired to realize a method for efficiently eluting and recovering gold and silver in activated carbon without using a cyan solution.

  In addition, the acid leaching method, which is one of the methods for leaching gold with high efficiency without using cyan, requires a strong oxidizing agent because gold is inactive, and the leaching cost is high. In addition, in order to leach gold in the metal-containing sulfide metal ore, it is necessary to sufficiently leach the main component metal sulfide ore so that the gold and the leachate can sufficiently come into contact with each other. Thus, even if gold in primary copper sulfide or pyrite is dissolved, the concentration of gold leached into the solution is considerably lower than when cyan is used.

  Therefore, even in the case of acid leaching, it is necessary to further concentrate gold by an adsorption method or a solvent extraction method in the subsequent process. In the adsorption method, activated carbon is known as an adsorbent, but it is necessary to use cyan for elution of gold adsorbed by gold alone. When cyan is not used, the activated carbon is incinerated to recover gold, which is more expensive than the case of elution. Further, the adsorbent as shown in Patent Document 6 has not been put into practical use due to problems such as high cost or inability to repeatedly use it.

  In the case of solvent extraction, extraction, settling and back-extraction facilities are required, and the gold concentration is very low, but there are many impurities other than gold, so the selective extraction rate of gold is a problem, making it easier and more convenient. An operable adsorption method is preferred.

  The present inventor conducted research to solve the above-mentioned problems. After leaching the metal sulfide ore with a halogen bath, leaching gold and silver together with the main component metal, and adsorbing the gold / silver leaching solution on the activated carbon. , By elution using an aqueous thiosulfate solution maintained at a predetermined pH, gold contained in the metal sulfide ore is efficiently adsorbed on activated carbon, and gold and silver adsorbed on the activated carbon are efficiently eluted. I found that I can do it.

  The present invention completed in the background of the above findings is, in one aspect, from an acid-containing and silver sulfide metal ore using an acidic leachate containing chloride ions and / or bromide ions as anions and copper and iron as cations. A step of warming and leaching gold and silver in the acidic leachate, a step of adsorbing at least gold and silver in the acidic leachate to activated carbon, and thiosulfuric acid maintained at a pH of less than 7 with respect to activated carbon on which at least gold and silver are adsorbed A method for eluting gold and silver, comprising a step of eluting gold and silver using an aqueous salt solution.

  In one embodiment of the gold and silver elution method of the present invention, the pH of the aqueous thiosulfate solution is maintained at 4 or more and less than 7.

  In another embodiment of the gold and silver elution method of the present invention, the thiosulfate aqueous solution is maintained at 20 to 90 ° C.

  In another embodiment of the gold and silver elution method of the present invention, the gold adsorbed on the activated carbon is selectively eluted and separated by maintaining the thiosulfate aqueous solution at 60 to 90 ° C.

  In yet another embodiment of the gold and silver elution method of the present invention, the silver adsorbed on the activated carbon is selectively eluted and separated by maintaining the thiosulfate aqueous solution at 20 to 50 ° C.

  In another embodiment of the gold and silver elution method of the present invention, the aqueous thiosulfate solution is an aqueous sodium thiosulfate solution.

  In still another embodiment of the gold and silver elution method of the present invention, the metal-containing / silver sulfide metal ore is from chalcocite, chalcopyrite, copper indigo, chalcopyrite, pyrite, arsenite, and arsenite. A concentrate containing at least one selected from the group consisting of:

  In yet another embodiment of the method for eluting gold and silver according to the present invention, the metal-containing / silver sulfide metal ore contains copper, iron, or arsenic as a main component metal using an acidic leachate from the concentrate. It is a leaching residue containing gold obtained by solid-liquid separation after leaching 80% or more.

In another embodiment of the gold and silver elution method of the present invention, the acidic leachate contains 40 to 200 g / L of chloride ions and 20 to 100 g / L of chloride ions when chloride ions are contained. It contains L bromide ions, 5-25 g / L copper, and 0.01-10 g / L iron, and has a pH of 0-1.9.

  In another embodiment of the method for eluting gold and silver according to the present invention, the warm leaching is performed at 60 to 100 ° C.

  In another aspect, the present invention is a method for recovering gold and silver from an aqueous thiosulfate solution containing gold and silver obtained by the gold and silver elution method of the present invention.

  According to the present invention, gold contained in a sulfide metal ore can be efficiently adsorbed on activated carbon, and gold and silver adsorbed on the activated carbon can be efficiently eluted.

3 is a flowchart of a gold and silver elution method according to an embodiment of the present invention. 6 is a graph showing the amount of Ag adsorption on activated carbon with respect to the liquid passing time obtained in Example 2. 6 is a graph showing the Au concentration in the liquid with respect to the elution time obtained in Example 3. 4 is a graph showing Ag concentration in liquid with respect to elution time obtained in Example 3. FIG. 6 is a graph showing the concentration of gold obtained in Example 4 in liquid. 4 is a graph showing the concentration of silver obtained in Example 4 in liquid.

  FIG. 1 shows a flowchart of a gold and silver elution method according to an embodiment of the present invention. In the elution method of gold and silver according to the present invention, gold and silver are contained from a metal-containing / silver sulfide metal ore using an acidic leachate containing chloride ions and / or bromide ions as anions and copper and iron as cations. Gold leaching using an aqueous thiosulfate solution maintained at a pH of less than 7 for the activated leachate, the step of adsorbing at least gold and silver in the acid leachate to the activated carbon, and the activated carbon to which at least gold and silver are adsorbed And elution of silver.

  Gold is often contained in trace amounts as a simple substance in sulfide metal ores such as chalcocite, chalcopyrite, copper indigo, chalcopyrite, pyrite, arsenite, arsenite. For this reason, in order to collect this, it is preferable to first concentrate the metal sulfide ore by crushing and then concentrating it by a flotation method. In addition, it is possible to further concentrate gold to the leaching residue by solid-liquid separation after leaching 80% or more of the main component metals copper, iron, or arsenic using acidic leachate from this concentrate, Processing efficiency is improved.

  As a method for leaching gold contained in this metal sulfide or gold concentrated in the leaching residue after leaching the concentrate or the main metal component as a more preferable form, strong oxidizing properties such as aqua regia A method of leaching with acid and a method of leaching with cyanide are known, but both have problems in terms of environmental load and safety. In particular, cyan leaching is a technique that can be avoided because its use is not limited by the high toxicity of cyan.

  When leaching with a strong oxidizing acid, there is no appropriate method for further concentrating the dissolved gold, and elution occurs when gold is adsorbed on an adsorbent such as activated carbon or functional resin, which is a well-known adsorbent. There is a problem, and if the entire adsorbent is incinerated and collected, the cost will rise significantly. It is said that the reason for this elution failure is that the halogenated complex when gold is leached with a strong acid is reduced to a simple substance when adsorbed on activated carbon.

However, it is described in Non-Patent Document 1 below that a polysulfide complex is formed when gold is leached under special conditions.
(Non-Patent Document 1) ME Berndt, T. Buttram, D. Earley III, WE Seyfried Jr., Geochimica et Cosmochimica Acta, 58, (2), 587-594, 1994
Gold polysulfide complexes are more stable than halogen complexes and are not easily reduced to single gold even when adsorbed on an adsorbent.

  On the other hand, the present invention does not require special conditions such as those described in Non-Patent Document 1, and gold is leached with a polysulfide complex that is easily adsorbed on activated carbon, and the gold adsorbed on the activated carbon is an aqueous thiosulfate solution. It is easily eluted and collected.

  In the present invention, first, gold is heated and leached from the metal-containing / silver sulfide metal ore into an acidic leaching solution using an acidic leaching solution containing chloride ions and / or bromide ions as anions and copper and iron as cations. . The leaching temperature is preferably 60 to 100 ° C. The acidic leachate preferably has a pH of 0 to 1.9. If the leaching temperature and the pH of the leaching solution are within such ranges, gold leaching is better.

  The acidic leachate preferably contains 20 to 200 g / L of chloride ions and bromide ions, and 0.01 to 30 g / L of copper and iron, respectively. Furthermore, the acidic leachate preferably contains 40-200 g / L chloride ions, 20-100 g / L bromide ions, 5-25 g / L copper, and 0.01-10 g / L iron. . By limiting the composition of the acidic leaching solution in this way, it is possible to satisfactorily dissolve chalcopyrite, arsenite, etc., which are difficult to dissolve in acid. Further, when bromine is contained, there is an effect that the dissolved gold is stabilized by Au (I).

  In the warm leaching step, the metal sulfide is dissolved in the acidic leaching solution to leach valuable metals. Trace amounts of gold and silver are leached together with the main metal. If necessary, after the solid-liquid separation, the gold and silver contained in the residue are leached with an acidic liquid having the same composition.

  Next, gold and silver in the acidic leachate are brought into contact with activated carbon and adsorbed. Contact of gold and silver with activated carbon may be performed by batch batch type or by continuously passing acidic leachate through an adsorption tower packed with activated carbon.

  After adsorbing gold and silver on activated carbon, it is necessary to adsorb the gold form as a polysulfide complex in order to facilitate elution. For this purpose, the presence of S (-II) is essential during leaching. In the case of the present invention, various metal sulfide species correspond to this.

  Although there are various kinds of activated carbon such as coconut shell activated carbon and coke activated carbon, those derived from any raw material may be used.

  In the present invention, an aqueous sodium thiosulfate solution maintained at a pH of less than 7 is used as an eluent. Examples of the thiosulfate include sodium thiosulfate, potassium thiosulfate and the like. Particularly, sodium thiosulfate is effective for elution of gold and silver. When sodium thiosulfate is less than pH 7, it is partially decomposed to produce sulfur.

  The aqueous thiosulfate solution elutes gold and silver in activated carbon, and precipitates the eluted silver as silver sulfide. The precipitated silver sulfide can be recovered from the eluent and treated with a chemical reduction method or the like to recover single silver.

  On the other hand, gold is eluted by an aqueous thiosulfate solution, but is a metal that does not form sulfides, and therefore remains eluted in the eluent. If necessary, gold can also be recovered from the eluent as a single gold using a chemical reduction method or a solvent extraction-electrolytic collection method.

  For elution of gold and silver from the activated carbon, it is preferable to adjust the concentration of thiosulfate ions with respect to the amount of gold and silver ions to be eluted. In particular, since sulfur is required when silver ions are precipitated, it is desired to decompose a considerable amount of thiosulfate ions. If it decomposes too much, sulfur will adsorb on the activated carbon and hinder the elution of gold and silver. Specifically, the concentration of thiosulfate ions in the thiosulfate aqueous solution can be 0.01 to 1.0 mol / L. The elution effect is saturated at a thiosulfate ion concentration of 0.5 mol / L. Naturally, the amount of thiosulfuric acid required varies depending on the amount of gold or silver adsorbed on the activated carbon, but even if elution is insufficient as described above, gold or silver is not lost. Addition of a large excess of thiosulfuric acid inhibits elution by covering the surface of the activated carbon with sulfur, so the realistic thiosulfuric acid concentration is 0.01 to 0.5 mol / L.

  The thiosulfate aqueous solution used for the eluent is kept at a pH of less than 7, preferably at a pH of 4 or more and less than 7, and more preferably at a pH of 4.5 or more and less than 6. By keeping the sodium thiosulfate aqueous solution below pH 7, the generation of sulfur by decomposition of thiosulfate ions is promoted, and the eluted silver precipitates with good sulfide formation.

  It is desirable to adjust the elution temperature with respect to the thiosulfate ion concentration. The decomposition of thiosulfate ions is promoted by setting the temperature to 20 to 90 ° C. In order not to interfere with the elution of both gold and silver, elution under low temperature conditions is preferred when the concentration of thiosulfate ions is low in order to prevent adsorption of sulfur onto activated carbon. Moreover, if it is close to normal temperature, it will become possible to selectively elute and separate silver from gold and silver adsorbed on the activated carbon. From such a viewpoint, the elution temperature is more preferably adjusted to 20 to 50 ° C. On the other hand, from the viewpoint of improving the separation performance of gold and silver, a higher temperature is preferable, and specifically, 60 to 90 ° C. is more preferable. By maintaining the aqueous thiosulfate solution at 60 to 90 ° C. in this way, gold adsorbed on the activated carbon can be selectively eluted and separated.

  After selectively eluting silver as described above from the activated carbon on which gold and silver are adsorbed, the remaining gold can be eluted from the activated carbon. Specifically, the activated carbon on which gold and silver are adsorbed is immersed in a thiosulfate aqueous solution (eluent) having a pH of less than 7 maintained at 20 to 50 ° C. to selectively elute silver. Subsequently, the supernatant of the eluent containing the eluted silver component is recovered. Next, the eluent is heated and maintained at 60 to 90 ° C., and the remaining gold is eluted from the activated carbon and similarly recovered. Thereby, silver and gold | metal | money can be favorably isolate | separated and collect | recovered from the activated carbon which gold | metal | money and silver adsorb | sucked.

  Furthermore, after the gold is selectively eluted from the activated carbon on which gold and silver are adsorbed as described above, the remaining silver can be subsequently eluted from the activated carbon. Specifically, the activated carbon on which gold and silver are adsorbed is immersed in a thiosulfate aqueous solution (eluent) of less than pH 7 maintained at 60 to 90 ° C. to selectively elute gold. Subsequently, the supernatant of the eluent containing the eluted gold component is recovered. Next, the eluent is cooled and maintained at 20 to 50 ° C., and the remaining silver is eluted from the activated carbon and similarly recovered. Thereby, silver and gold | metal | money can be favorably isolate | separated and collect | recovered from the activated carbon which gold | metal | money and silver adsorb | sucked.

  Moreover, the activated carbon of the present invention can be used repeatedly for adsorption of silver and gold even after elution of silver and gold, which is advantageous in terms of cost.

  According to the above-described separation method of the present invention, gold and silver adsorbed on activated carbon can be efficiently eluted by a simple operation of setting pH using an aqueous thiosulfate solution as an eluent.

  Examples of the present invention are shown below, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
35 g of gold sulfide-containing concentrate (Cu: 17% by mass, Fe: 27% by mass, S: 25% by mass, Au: 90 ppm, main ore types are chalcopyrite and pyrotite Fe _1-x S) / L. The leachate contained Cl ⁻ : 180 g / L, Br ⁻ : 20 g / L, Cu ²⁺ : 18 g / L, Fe ³⁺ : 2 g / L, and the pH was 1.5. The leachate was heated to 85 ° C. and stirred while blowing 0.1 L per minute. The leachate having a gold concentration of 2 mg / L or more thus obtained was passed through a column packed with coconut shell-derived activated carbon (coconut MC manufactured by Taihei Chemical Sangyo Co., Ltd.) to adsorb gold onto the activated carbon. The gold concentration of the leachate after passing through the column was less than 0.1 mg / L.
When the gold concentration of the activated carbon in the column reached about 7000 g / ton, it was taken out from the column. The amount of gold adsorbed was quantified by an ash blowing method and ICP-AES, and it was 7500 g / ton.

(Example 2)
Metal sulfide concentrates containing silver (Cu: 17% by mass, Fe: 27% by mass, S: 25% by mass, Ag: 0.03% by mass, main ore species are chalcopyrite and pyrotite Fe _1-x S), It weighed so that it might become 35 g / L with respect to a leaching solution. The leachate contained Cl ⁻ : 180 g / L, Br ⁻ : 20 g / L, Cu ²⁺ : 18 g / L, Fe ³⁺ : 2 g / L, and the pH was 1.0. The leachate was heated to 65 ° C. and stirred while blowing air of 0.1 L per minute. The obtained leachate having a silver concentration of 10 mg / L or more was passed through a column packed with coconut shell-derived activated carbon (coconut MC manufactured by Taihei Chemical Sangyo Co., Ltd.) in a batch manner to adsorb silver onto the activated carbon. The silver concentration of the leachate after passing through the column was less than 0.1 mg / L.
The adsorption amount (mg) of Ag on the activated carbon was quantified by the ash spray method and ICP-AES for each predetermined flow time. In FIG. 2, the graph which concerns on Ag adsorption amount to activated carbon with respect to the liquid passing time obtained in Example 2 is shown.

Example 3
Activated carbon (coconut shell-derived activated carbon: coconut granular charcoal manufactured by Taihei Chemical Sangyo Co., Ltd.) adsorbed with gold from the leachate leached from the concentrate was prepared. The Au quality in the activated carbon was 9000 g / ton, and the Ag quality was 1400 g / ton. As an eluent, a 0.1 M sodium thiosulfate solution with pH = 4 was used. The temperature of the eluent was normal temperature (20-30 ° C.) and 80 ° C. The above-mentioned activated carbon was immersed in this eluent and stirred. Sampling was performed every hour from the start of the test, and the concentrations of gold and silver in the eluent were measured. The measurement was performed by ICP measurement. The results of the concentration of the obtained gold and silver in the liquid are shown in FIGS. 3 and 4, respectively. As shown in FIG. 3, it can be seen that when elution is performed at 80 ° C., gold is better eluted from activated carbon than silver. When elution was performed at 80 ° C., the Au concentration in the solution was 160 mg / L and the Ag concentration was <1 mg / L after 6 hours of elution. Elution at 80 ° C. not only separated gold and silver, but also improved the elution rate of Au. On the other hand, as shown in FIG. 4, when it elutes at normal temperature, it turns out that silver is eluting more favorably from activated carbon with respect to gold | metal | money. When elution was performed at room temperature, the Au concentration in the solution was 20 mg / L and the Ag concentration was 25 mg / L after 6 hours of elution. As for silver, all the silver in the activated carbon was eluted.

Example 4
Activated carbon (coconut shell-derived activated carbon: coconut granular charcoal manufactured by Taihei Chemical Sangyo Co., Ltd.) adsorbed with gold from the leachate leached from the concentrate was prepared. The Au quality in the activated carbon was 9000 g / ton, and the Ag quality was 1400 g / ton. As eluents, 0.1M sodium thiosulfate solutions with pH = 4, 6, 8 were used, respectively. The temperature of the eluent was 80 ° C. The above-mentioned activated carbon was immersed in this eluent and stirred. Sampling was performed every hour from the start of the test, and the concentrations of gold and silver in the eluent were measured. The measurement was performed by ICP measurement. The results of the obtained gold and silver concentrations in the liquid are shown in FIGS. 5 and 6, respectively. As shown in FIGS. 5 and 6, when elution was performed with an eluent having a pH of 8, elution of both gold and silver was poor.

Claims (11)

Using an acidic leachate containing chloride ions and / or bromide ions as anions and copper and iron as cations, heating and leaching gold and silver from the metal-containing / silver sulfide metal ore into the acid leachate;
Adsorbing at least gold and silver in the acidic leachate on activated carbon;
Elution of gold and silver using an aqueous thiosulfate solution maintained at a pH of less than 7 with respect to activated carbon on which at least gold and silver are adsorbed;
Elution method for gold and silver.   The gold and silver elution method according to claim 1, wherein the pH of the aqueous thiosulfate solution is maintained at 4 or more and less than 7.   The gold and silver elution method according to claim 1 or 2, wherein the aqueous thiosulfate solution is maintained at 20 to 90 ° C.   The gold and silver elution method according to claim 3, wherein gold adsorbed on the activated carbon is selectively eluted and separated by maintaining the aqueous thiosulfate solution at 60 to 90 ° C.   The method for eluting gold and silver according to claim 3, wherein the silver adsorbed on the activated carbon is selectively eluted and separated by maintaining the aqueous thiosulfate solution at 20 to 50 ° C.   The gold and silver elution method according to claim 1, wherein the aqueous thiosulfate solution is an aqueous sodium thiosulfate solution.   The metal-containing / silver sulfide metal ore is a concentrate containing at least one selected from the group consisting of chalcocite, chalcopyrite, copper indigo, chalcopyrite, pyrite, arsenite, and arsenite. 7. The elution method of gold and silver according to any one of 6.   The metal-containing / silver sulfide metal ore contains gold obtained by solid-liquid separation after leaching 80% or more of copper, iron, or arsenic which is a main component metal from the concentrate using an acidic leachate. The method for eluting gold and silver according to claim 7, which is a leaching residue. When the acidic leachate contains chloride ions, 40-200 g / L chloride ions, when it contains bromide ions, 20-100 g / L bromide ions, 5-25 g / L copper, and 0.01 The method for eluting gold and silver according to claim 1, comprising 10 to 10 g / L of iron and having a pH of 0 to 1.9.   The gold and silver elution method according to claim 1, wherein the warm leaching is performed at 60 to 100 ° C.   The method of collect | recovering gold | metal | money and silver from the thiosulfate aqueous solution containing the gold | metal | money and silver obtained by the elution method of gold | metal | money in any one of Claims 1-10.

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