JP4403259B2 - Method for recovering platinum group elements - Google Patents

Description

  The present invention is a platinum group element recovery for recovering a platinum group element from a leachate obtained by leaching nitric acid to an object containing gold, silver and a platinum group element, such as silver electrolysis slime, and a gold electrolysis solution. Regarding the method.

Hereinafter, the background art will be described by taking, as an example, a case where silver electrolytic slime is used as an object to be processed containing gold, silver, and a platinum group element. (For example, see Patent Document 1)
The silver electrolysis slime generated in the silver electrolysis (step S100) in FIG. 3 contains gold, silver, and a platinum group element (platinum, palladium, etc.) in a concentrated manner. Therefore, the silver electrolysis slime is leached with nitric acid (step S101), the silver and platinum group elements in the silver electrolysis slime are leached into the leaching solution, and gold electrolysis is performed using the gold electrolysis anode obtained from the leaching residue. Gold is refined by step S102).

  Most of the platinum group elements migrate to the nitric acid leaching solution and are concentrated, but some of the platinum group elements that have migrated to the nitric acid leaching residue are eluted from the gold electrolytic anode during gold electrolysis (step S102). It moves to the post-electrolysis solution and is concentrated and contained. FIG. 4A shows an example (g / l) of each content of gold, palladium, and platinum in the gold electrolysis solution.

  The platinum group element concentrated in the solution after gold electrolysis adheres to the electrodeposited gold when the concentration increases, thereby reducing the purity of the electrodeposited gold. For this reason, copper and zinc are added to the gold electrolysis solution, and the platinum group elements are reduced and recovered together with gold from the gold electrolysis solution by cementation (step S103), and the reduction recovery product is returned to the nitric acid leaching process. Yes.

  On the other hand, the nitric acid leaching solution contains silver and platinum group elements. Therefore, for example, as described in Patent Document 1, sodium chloride (or hydrochloric acid) is added to carry out salting out (step S104), and silver is recovered as silver chloride. A reducing agent such as zinc powder is added to the post-salting solution for reduction (step 105) to form a precipitate containing a platinum group element, which is filtered and washed. FIG. 4 (B) shows that after removing silver chloride by carrying out salting out, zinc powder twice the equivalent of platinum group element was added for reduction, and after stirring for 1 hour, palladium and platinum were filtered. An example of a reduction rate is shown. It can be seen that 95% or more of palladium and 90% of platinum in the solution after salting out were reduced. Then, the reduced platinum group element becomes a precipitate.

  The precipitate containing the platinum group element is filtered and washed as described above, and then added with aqua regia (step S106) to dissolve, and further evaporated to dryness to evaporate nitric acid (step S107) to dry. Then, hydrochloric acid is added to the dried solid and dissolved (step S108) to obtain a hydrochloric acid solution of platinum group element.

Ammonium chloride is added to the platinum group hydrochloric acid solution to recover platinum as ammonium chloroplatinate (S109), ammonia is added to the back solution, and hydrochloric acid is further added to recover palladium as a palladium complex salt ( In step S110), other platinum group elements are recovered by reducing the post-solution with zinc or the like (step S111).
JP-A-9-263847 (2nd page)

  However, as shown in step S103, when the reduced and recovered gold and platinum group elements recovered from the gold electrolysis solution are returned to the nitric acid leaching step (step S101), the efficiency of nitric acid leaching is reduced and the leaching residue is reduced. A considerable amount of platinum group element remains, and after the platinum group element has transferred to the gold electrolysis anode, it is eluted in a large amount from the gold electrolysis anode into the gold electrolysis solution. For this reason, the amount of platinum group element retention in the gold electrolysis process increases, and the number of times the gold electrolysis solution is purified to remove the impurity metal elements in the gold electrolysis solution, resulting in an increase in cost. Resulting in.

In addition, returning the gold electrolysis solution to the nitric acid leaching step as described above complicates the step, and as a result, the yield of platinum group element recovery also decreases.
Furthermore, in the above-mentioned background art, aqua regia is added to the precipitate obtained after reducing the solution after salting out (step S105) (step S106) to dissolve it, and further evaporated to dryness (step S107). And nitric acid, which is a problem in the subsequent process, was removed by dissolving hydrochloric acid (step S108). And this denitration process needs to be repeatedly performed depending on the case, and the aqua regia treatment and the denitration process take a long time.

  The object of the present invention has been made in consideration of the above-mentioned circumstances, and can reduce the retention amount of platinum group elements in the process and the number of times the gold electrolysis solution is cleaned, and simplify the process to improve the yield. Another object of the present invention is to provide a platinum group element recovery method that can be used. Another object of the present invention is to provide a platinum group element recovery method capable of recovering a platinum group element in a short time without the necessity of performing a long time aqua regia treatment and a denitration step.

  According to the first aspect of the present invention, an object to be treated containing gold, silver and a platinum group element is leached with nitric acid, and gold is deposited and purified by gold electrolysis using an anode for gold electrolysis obtained from the leaching residue. A platinum group element recovery method for recovering a platinum group element contained in each of the gold electrolysis step after the gold electrolysis step and the nitric acid leaching step, wherein a reducing agent is added to the gold electrolysis solution. Then, gold is reduced, and gold is recovered as reduced gold, and a platinum group element contained in the solution after reduction is recovered.

  The invention according to claim 2 is the invention according to claim 1, wherein the leaching solution in the nitric acid leaching step is mixed with the post-reduction solution obtained by recovering the reduced gold from the post-gold electrolysis solution, and subjected to salting-out treatment. In addition to recovering silver, the platinum group element is recovered from the post-salting solution containing the platinum group element.

  The invention according to claim 3 is the invention according to claim 2, wherein the post-salting solution in which silver chloride is recovered by the salting-out treatment is made alkaline, and then a reducing agent is added to neutralize and reduce, The platinum group element is recovered from the platinum group element-containing material obtained by neutralization reduction.

According to a fourth aspect of the present invention , an object to be treated containing gold, silver and a platinum group element is leached with nitric acid, and the leachate is salted out to recover silver chloride. In the method for recovering the platinum group element to be recovered, the post-salting solution is made alkaline and then neutralized by adding a reducing agent, and the platinum group element is recovered from the platinum group element-containing material obtained by this neutralization reduction. It is characterized by doing.

A fifth invention is, or claim 3 in the invention described in the fourth invention, the hydrochloric acid leach after drying the platinum group element-containing substance, the hydrochloric acid solution of platinum group elements obtained by the hydrochloric acid leaching The platinum group element is recovered.

  According to the first aspect of the present invention, the reducing agent is added to the gold electrolysis solution to reduce the gold, and the gold is recovered as reduced gold, and the platinum group element contained in the post-reduction solution is recovered. Therefore, since the reduction recovery of gold and platinum group elements is not returned to the nitric acid leaching process, the amount of platinum group elements during nitric acid leaching increases, so that the nitric acid leaching efficiency decreases. Can be prevented from staying in the process and increasing the number of times of cleaning the gold electrolysis solution.

  Moreover, since the reduction | restoration collection | recovery of gold | metal | money and a platinum group element is not returned to a nitric acid leaching process, the simplification of a platinum group element recovery process can be implement | achieved and the yield of platinum group element recovery can be improved.

  According to the invention described in claim 2, since the reduced liquid obtained by recovering the reduced gold from the gold electrolysis liquid contains chlorine ions, the post-reduction liquid is mixed with the leachate in the nitric acid leaching step. By carrying out the salting-out treatment, it is not necessary to add sodium chloride or the like for the amount of the contained chlorine ions for carrying out the salting-out, and the cost can be reduced.

According to the invention described in claim 3 or 5, the post-salting solution in which silver chloride is recovered and the platinum group elements are concentrated by salting-out is made alkaline, and then a reducing agent is added to neutralize the solution. The platinum group element-containing material is reduced by this neutralization reduction. Since this platinum group element-containing material is a finely divided metal, it takes a long time after neutralization and reduction, and the operation is complicated. Since it is not necessary to carry out the denitration step, the platinum group element can be easily recovered from the precipitate containing the platinum group element in a short time.

According to the invention described in the fourth or fifth invention , the leachate obtained by leaching the object to be treated is subjected to salting-out treatment, and after the salting-out solution is made alkaline, the reducing agent is added to neutralize and reduce, The platinum group element is recovered after removing residual nitrate ions and nitrite ions from the platinum group element-containing material obtained by the neutralization reduction. Since this platinum group element-containing material is a finely divided metal, Since it is not necessary to carry out the aqua regia treatment and denitration process that require a long time after the reduction and the operation is complicated, the platinum group element can be easily recovered from the precipitate containing the platinum group element in a short time.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings, taking as an example the case of using silver electrolytic slime as an object to be processed.
FIG. 1 is a flowchart showing an embodiment of the platinum group element recovery method according to the present invention.

  In the non-ferrous smelting process, copper, silver, gold, platinum and the like are generally purified sequentially. For copper, copper anode is obtained from ore and recycled raw materials through copper smelting process, copper electrolysis process is carried out using this copper electrolysis anode, and copper is deposited on the cathode to refine copper. To do.

  Since the copper electrolysis slime produced by the copper electrolysis process is concentrated with noble metal elements such as gold and silver and platinum group elements such as platinum and palladium, silver is then purified. That is, the copper electrolysis slime is converted into a silver electrolytic anode through a fine silver process, and the silver electrolysis process (step S1) shown in FIG. 1 is performed to deposit silver on the cathode and purify the silver.

  Silver electrolysis slime produced by silver electrolysis contains, for example, about 60% gold, about 25% silver, and about 15% platinum group elements such as platinum and palladium. Therefore, in order to purify gold, in order to separate silver and platinum group elements from the silver electrolysis slime, a nitric acid leaching (parting) process is performed in which the silver electrolysis slime reacts with nitric acid in the leaching tank (step). S2) The silver and platinum group elements in the silver electrolytic slime are leached into nitric acid and recovered.

  The leaching residue obtained by the nitric acid leaching is filtered and washed, dried, and then cast into a gold electrolytic anode. A gold electrolysis process is performed by the so-called “Wholwill” method using this gold electrolysis anode (step S3), and gold is deposited on the cathode to purify the gold.

  Most of the platinum group elements in the silver electrolysis slime are transferred to the leachate in the nitric acid leaching step (step S2) and concentrated, but some of the platinum group elements transferred to the leaching residue are subjected to gold electrolysis through the gold electrolysis anode. It is eluted and concentrated in the back solution. An example of each content (g / l) of gold, palladium and platinum in this gold electrolytic solution is shown in FIG.

  Furthermore, in this Embodiment, 1-5 times amount (preferably 1-3 times amount) of reducing agents, for example, ferrous sulfate, after the said gold electrolysis are equivalent to the gold | metal equivalent contained in this gold electrolysis post-solution. It is added to the liquid, and gold is reduced (step S4) to be precipitated, which is filtered and washed to recover gold as reduced gold. Since platinum group elements are not reduced by ferrous sulfate, they are hardly contained in the reduced gold, and are transferred to the post-reduction solution and concentrated. That is, the ferrous sulfate is a reducing agent having an ORP potential in the range of 500 to 800 mV that reduces gold but does not reduce platinum group elements. Similar reducing agents include oxalic acid and sulfurous acid in addition to the ferrous sulfate.

  FIG. 2 (B) shows a reduction after adding ferrous sulfate twice the equivalent of gold contained in the gold electrolysis solution to the gold electrolysis solution and filtering after stirring for 3 hours. An example (g / l) of the content of gold, palladium, and platinum contained in the liquid is shown. Compared with FIG. 2A, it can be seen that the gold content is reduced in the solution after reduction, and the platinum group elements are sufficiently concentrated.

  By the way, the gold electrolysis post-solution in the gold electrolysis step generally contains about 100 g / l of gold and about 100 g / l of hydrochloric acid. Therefore, a large amount of hydrochloric acid is also contained in the post-reduction liquid obtained by recovering the reduced gold from the post-gold electrolysis liquid. Therefore, the leaching solution in the nitric acid leaching step in step S2 is mixed with the post-reduction solution to salt out silver present in the leaching solution (step S5), and silver is recovered as silver chloride after filtration and washing. Platinum group elements are scarcely contained in silver chloride and migrate to the solution after salting out and concentrated.

  At the stage of adding caustic soda (NaOH) to the post-salting solution to make the post-salting solution alkaline with a pH of 7 or more, a reducing agent is added to the post-salting solution, and the post-salting solution is subjected to ORP potential − Neutralizing and reducing to 100 mV or less (step S6), a precipitate is obtained. Thereafter, the precipitate is filtered and washed to obtain a platinum group element-containing material that is a concentrate of the platinum group element. Examples of the reducing agent include sodium boron hydride (NaBH) that is alkaline and exhibits a reducing effect. The platinum group element is hardly contained in the solution after neutralization reduction, and is concentrated to the platinum group element-containing material.

  FIG. 2 (C) shows a case where caustic soda is added to the post-salting solution to make the post-salting solution alkaline with a pH of 9, and sodium boron hydride is added to the post-salting solution so that the ORP potential is -200 mV. An example of the reduction ratio of palladium and platinum when the mixture is reduced and the precipitate after salting out is filtered and washed after stirring for 1 hour to obtain a platinum group element-containing precipitate is shown. It can be seen that 95% or more of palladium and platinum are reduced to a platinum group element-containing material.

  The platinum group element-containing material is dried at 200 to 400 ° C. to decompose and remove the adhering liquid, residual nitrate ions and residual nitrite ions (step S7). Thereby, the platinum group element containing material from which the residual nitrate ions and nitrite ions have been removed can be recovered. The recovered platinum group element-containing material is finely divided metal.

  Thereafter, the dried platinum group element-containing material is slurried with hydrochloric acid 4 times or more equivalent to the platinum group element, heated to 70 to 90 ° C., and leached with hydrochloric acid for 1 hour or more (step S8). Filter and wash to separate and recover the platinum group element hydrochloric acid solution. Platinum group elements are scarcely contained in the leaching residue during hydrochloric acid leaching, and are concentrated and recovered in a hydrochloric acid solution.

  FIG. 2D shows that after the platinum group element-containing material is dried at 300 ° C. for 20 hours, hydrochloric acid at least four times the equivalent of the platinum group element is added to the platinum group element-containing material, and the slurry concentration is 20%. An example of the leaching rate of hydrochloric acid of palladium and platinum is shown in the case of adding so that hydrochloric acid is leached at 80 ° C. for 3 hours, cooled to room temperature, and filtered and washed. It can be seen that 95% or more of any platinum group element is leached in hydrochloric acid and dissolved in the hydrochloric acid solution.

  Ammonium chloride is added to this platinum group hydrochloric acid solution to recover platinum as ammonium chloroplatinate (step S9), ammonia is added to the back solution, and hydrochloric acid is further added to recover palladium as a palladium complex salt. (Step S10) The other platinum group elements are recovered by reducing the rear solution with zinc powder or the like (step S11). Alternatively, a selective separation method using an electrolytic purification method, a solvent extraction method, an ion exchange resin method, a SuperLig (registered trademark) method using MRT (Molecular Recognition Technology), etc. from the platinum group element hydrochloric acid solution is performed. Thus, platinum group elements may be recovered for each element.

  As described above, according to the above embodiment, a reducing agent such as ferrous sulfate is added to the gold electrolysis solution to reduce gold, and gold is recovered as reduced gold and concentrated to the solution after reduction. Since the collected platinum group element is not recovered, the reduction and recovery of gold and platinum group element is not returned to the nitric acid leaching process, so the amount of platinum group element increases at the time of nitric acid leaching. As a result, it is possible to prevent platinum group elements from staying in the gold electrolysis process and increasing the number of times the gold electrolysis solution is purified, thereby reducing costs.

  Moreover, since the reduction | restoration collection | recovery of gold | metal | money and a platinum group element is not returned to a nitric acid leaching process, the simplification of a platinum group element recovery process can be implement | achieved and the yield of platinum group element recovery can be improved.

  In addition, since the reduced liquid obtained by recovering the reduced gold from the gold electrolysis liquid contains chlorine ions, the post-reduction liquid is mixed with the leachate in the nitric acid leaching step and subjected to salting-out treatment. For salting out, sodium chloride or the like need not be added in an amount corresponding to the amount of contained chlorine ions, and the cost can be reduced.

  Furthermore, the solution after the salting out in which the silver chloride is removed by the salting-out treatment and the platinum group element is concentrated is made alkaline, and then the reducing agent (NaBH) is added to neutralize and reduce, and this neutralization reduction causes the platinum group. The platinum group element is obtained by obtaining element-containing materials and decomposing residual nitrate ions and nitrite ions by drying, eliminating the need for aqua regia treatment and denitration processes that require a long time and are complicated to operate. The platinum group element can be easily recovered from the inclusions in a short time.

As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.
For example, salting out a leachate obtained by leaching silver electrolytic slime with nitric acid is performed by adding a substance containing chlorine such as sodium chloride or hydrochloric acid, and the post-salting solution obtained by removing silver chloride by this salting-out is made alkaline. Then, a reducing agent may be added for neutralization reduction, and the platinum group element may be recovered from the obtained platinum group element-containing material in the same manner as in the above embodiment.

  Also in this case, the platinum group element obtained by salting out the leachate obtained by leaching silver electrolytic slime with nitric acid, making the post-salting solution alkaline, and then neutralizing and reducing by adding a reducing agent. Since the platinum group element is recovered from the inclusion, it is not necessary to carry out aqua regia treatment that requires a long time after neutralization reduction and is complicated in operation. Can be recovered.

It is a flowchart which shows one Embodiment in the collection | recovery method of the platinum group element which concerns on this invention. (A) is a table | surface which shows an example of content of the gold | metal | money and platinum group element in the gold electrolysis post-solution in the flowchart of FIG. (B) is a chart showing an example of the concentrations of gold and platinum group elements in the post-reduction liquid after the gold electrolysis liquid is reduced with ferrous sulfate. (C) is a table | surface which shows an example of the reduction rate of the platinum group element by the neutralization reduction | restoration after salting-out implementation in the flowchart of FIG. (D) is a chart which shows an example of the reduction rate of a platinum group element when the platinum group element containing material is leached with hydrochloric acid in the flowchart of FIG. It is a flowchart which shows the collection | recovery method of the platinum group element in background art. (A) is a chart which shows an example of the concentration amount of the gold | metal | money and platinum group element in the gold electrolysis post-solution in the flowchart of FIG. (B) is a chart which shows an example of the reduction rate of the platinum group element by the reduction | restoration after salting-out implementation in the flowchart of FIG.

Claims (3)

After the gold electrolysis in the above gold electrolysis step, the object to be treated containing gold, silver and platinum group elements is leached with nitric acid, and gold is deposited by gold electrolysis using the anode for gold electrolysis obtained from the leaching residue. A platinum group element recovery method for recovering a platinum group element contained in the liquid and the leaching liquid in the nitric acid leaching step,
A method for recovering a platinum group element, comprising adding a reducing agent to the gold electrolysis liquid to reduce gold, recovering gold as reduced gold, and recovering a platinum group element contained in the liquid after reduction .   The post-reduction solution obtained by recovering the reduced gold from the post-electrolyzed gold solution is mixed with the leaching solution from the nitric acid leaching step for salting-out to collect silver as silver chloride, and the post-salting solution containing platinum group elements The platinum group element recovery method according to claim 1, wherein the platinum group element is recovered from the platinum group element.   The post-salting solution that recovered silver chloride by the salting-out treatment is made alkaline, and then neutralized by adding a reducing agent, and the platinum group elements are recovered from the platinum group element-containing material obtained by this neutralization reduction. The method for recovering a platinum group element according to claim 2.

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