JP2015193888A - Recovery method of platinum group element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method having an enhanced recovery ratio of selenium, rhodium, and ruthenium while suppressing reduction of tellurium.SOLUTION: In a recovery method of platinum group elements and selenium where selenium scum is precipitated by adding a reducer to an original liquid containing the platinum group elements, selenium, and tellurium, the selenium and the platinum group elements are reduced while suppressing reduction of the tellurium by setting a terminal concentration of selenium of 3 g/L-20 g/L in the original liquid. For example, an oxidation reduction potential of 520 mV-420 mV is set as a terminal point, or an oxidation reduction potential of 490 mV-470 mV is set as a terminal point in the presence of activated carbon in the recovery method of platinum group elements and selenium.

Description

The present invention relates to a method for effectively recovering a platinum group element together with selenium from a liquid containing a platinum group element such as copper electrolytic slime and selenium.

Copper electrolytic slime contains noble metals such as gold and silver and platinum group elements. Therefore, for example, this slum is wet treated to separate silver, and gold is solvent extracted from the remaining liquid. Since this gold-extracted solution still contains a large amount of selenium, tellurium and platinum group elements, the following methods for recovering selenium and platinum group elements from the gold-extracted solution are known.

(B) Sulfurous acid gas was blown into the liquid after copper extraction from copper electrolytic deposits under specific conditions to recover and recover the platinum group and gold, and after this was solid-liquid separated, the liquid was separated into sulfurous acid gas under specific conditions. Selenium is reduced and solidified by solid-liquid separation, and then sulfurous acid gas is blown into the liquid to perform tellurium reduction and hatching (Patent Document 1).
(B) After extracting gold from the leaching solution of copper electrolytic slime and adsorbing platinum group elements with an anion exchange resin, sodium bisulfite is added to the residual liquid after the adsorption, and the precipitate containing palladium is filtered. A method of separating and recovering selenium by blowing sulfur dioxide into the obtained filtrate (Patent Document 2).
(C) A method in which silver is iron-reduced and converted from the solution after gold solvent extraction and then melted, selenium is reduced with sulfurous acid and then distilled under reduced pressure, and platinum group elements are recovered by solvent extraction (Non-patent Document 1) .

JP 2001-316735 A JP 2012-126611 A

Establishment of copper starch wet processing technology, resources and materials vol.116, p484-492 (2000)

The conventional method has the following problems.
In the selenium reduction process, sulfurous acid gas is introduced into the solution containing selenium, tellurium, and platinum group elements to reduce selenium, and the platinum group elements containing rhodium and ruthenium are also reduced together and transferred to selenium soot. To do. At this time, in order to separate selenium and tellurium, the reduction of selenium is stopped to about 80% to suppress the reduction of tellurium. If the reduction of selenium proceeds too much (when the reduction oxidation potential of the liquid falls below a certain range), the reduction of tellurium proceeds rapidly and hatches, increasing the amount of tellurium soot mixed in the selenium soot.

Thus, since the reduction of selenium is performed so that the reduction oxidation potential does not become below a certain level, the reduction of the platinum group elements of rhodium and ruthenium does not proceed, and the recovery rate of the platinum group elements is limited to about 30 to 40%. There was a problem.

The recovery method of the present invention solves the above-mentioned problems of conventional methods, and suppresses the reduction of tellurium by determining the end point of the reduction reaction based on the difference in the reduction progress of selenium, tellurium, rhodium, and ruthenium. However, the present invention provides a recovery method in which the reduction of selenium, rhodium, and ruthenium is advanced to the ultimate to increase the recovery rate.

The present invention relates to a platinum group element and selenium recovery method that solves the above-described problems with the following configuration.
[1] In a method of precipitating selenium soot by adding a reducing agent to an original solution containing a platinum group element, selenium and tellurium, by proceeding with reduction at an end point of selenium concentration of 3 g / L to 20 g / L in the solution A method for recovering platinum group elements and selenium, comprising reducing reduction of tellurium and promoting reduction of selenium and platinum group elements.
[2] The method for recovering a platinum group element and selenium according to the above [1], in which the reduction proceeds with the oxidation-reduction potential of the original solution at 520 mV to 420 mV.
[3] The method for recovering a platinum group element and selenium according to the above [1], wherein the reduction proceeds in the presence of activated carbon with an oxidation-reduction potential of 490 mV to 470 mV as the end point.
[4] Recovery of platinum group element and selenium as described in [3] above, wherein 0.03 to 0.9 times the amount of activated carbon is added to the original liquid before the reduction and the reduction proceeds. Method.
[5] The method for recovering a platinum group element and selenium according to any one of [1] to [4], wherein the reduction is advanced under heating at a liquid temperature of 70 ° C. to 80 ° C.
[6] The platinum group element, selenium and tellurium-containing liquid is a gold extraction residue produced by wet treatment of copper electrolytic slime, and the platinum group element and selenium described in any one of [1] to [5] above Collection method.

[Specific description]
In the method of the present invention, a selenium soot is precipitated by adding a reducing agent to an original solution containing a platinum group element, selenium and tellurium, and the selenium concentration of the original solution is 3 g / L to 20 g / L as an end point. It is a platinum group element and selenium recovery method characterized in that the reduction of tellurium is suppressed and the reduction of selenium and the platinum group element is advanced by advancing the reduction.

As the original solution containing the platinum group element, selenium and tellurium, for example, a gold extraction residual solution generated by wet processing of copper electrolytic slime can be used. In addition, a solution obtained by adding selenium to a solution containing a platinum group element can be used as a raw material-containing solution. As the reducing agent added to the original solution, sodium sulfite, sulfurous acid gas, or the like can be used.

FIG. 1 shows the progress of reduction of selenium (Se) and tellurium (Te), rhodium (Rh) and ruthenium (Ru) in the liquid. In the illustrated example, the residual ratio of each element is 100% at an oxidation-reduction potential (ORP) of 645 mV (Ag / AgCl). Selenium decreases linearly in proportion to the lapse of the reduction time (decrease in ORP value), and the residual rate becomes about 1% after 480 minutes of reduction (ORP value of about 339 mV).

On the other hand, tellurium is slow to reduce even at a reduction of about 470 minutes (ORP value of about 350 mV), and the residual rate is about 85%. When the reduction time becomes longer and the ORP value becomes about 330 mV or less, the reduction rapidly proceeds. Similarly, the reduction of rhodium is slow until about 440 minutes (ORP value of about 420 mV), and the residual rate is about 78%, and when the reduction time becomes longer and the ORP value becomes about 400 mV or less, the reduction proceeds rapidly. . In addition, the reduction of ruthenium proceeds rapidly until the reduction is about 60 minutes (ORP value of about 554 mV), but the reduction is slow from about 60 minutes to about 480 minutes (ORP value of about 554 to about 340 mV), and the ORP value is higher than 339 mV. When it falls, the reduction proceeds rapidly.

As shown in the figure, the ORP value (X1) at which the reduction of tellurium begins to proceed abruptly is slightly lower than the ORP value (X2) at which the reduction of rhodium begins to proceed rapidly, and if the reduction proceeds until the ORP value reaches X1 (ORP) When the reduction proceeds with the value X1 as the end point), the reduction of selenium, rhodium, and ruthenium can proceed while the reduction of tellurium is suppressed.

In the method of the present invention, the reduction of selenium, rhodium and ruthenium is controlled while determining the end point of the reduction reaction based on the difference in the progress of reduction of selenium, tellurium, rhodium and ruthenium. This is a collection method that improves the collection rate by proceeding to the ultimate. Specifically, by reducing the selenium concentration from 3 g / L to 20 g / L, preferably from 4 g / L to 18 g / L, the reduction of tellurium is suppressed and the reduction of selenium and the platinum group element is advanced. .

For example, for a selenium concentration of 68 g / L, a tellurium concentration of 2.5 g / L, a rhodium concentration of 1.5 mg / L, and a ruthenium concentration of 36 mg / L, until the selenium concentration in the solution reaches 3 g / L to 20 g / L. As the reduction proceeds (when the selenium concentration is reduced from 3 g / L to 20 g / L as the end point), the selenium residual rate is approximately 4% to 29%, and as shown in FIG. 1, the redox potential of the original solution at this time Is in the range of about 520 mV to about 420 mV.

In this redox potential range, the residual ratio of tellurium is about 80% or more, and the reduction of tellurium hardly progresses, but rhodium is rapidly reduced when the redox potential ranges from about 470 mV to about 420 mV. The rate can be reduced to about 50%, and the reduction of ruthenium can proceed to a residual rate of about 55% to about 50%.

Furthermore, the recovery method of the present invention is shown in FIG. 1 while suppressing the reduction of tellurium when the reduction proceeds by adding activated carbon to the original solution and the oxidation-reduction potential of the original solution is 490 mV to 470 mV. It is possible to promote the reduction of rhodium and ruthenium more than the case, and to reduce the residual rate of these to increase the recovery rate of rhodium and ruthenium.

When activated carbon is used, the powder is most effective. Since the specific surface area is large, the contact between the liquid and activated carbon is increased, and the reaction proceeds. However, when powdered activated carbon is used, the activated carbon is likely to be mixed into the selenium soot, and when the selenium is distilled and recovered in the subsequent process, a gas caused by carbon is generated, causing a safety concern. Even if granular (about 1 to 10 mm) activated carbon is used, a sufficient effect can be obtained, and granular activated carbon is preferable.

The amount of activated carbon added is preferably 0.03 to 0.9 times the amount of selenium in the original solution. If this amount is less than 0.03 times, the effect is poor, and if it exceeds 0.9 times, the effect is limited.

In the conventional method, the liquid temperature is about 70 ° C, but in the method of the present invention, the liquid temperature is preferably 70 ° C to 80 ° C. By heating and increasing the liquid temperature, reduction of selenium, rhodium, and ruthenium can be further promoted.

The recovery method using the activated carbon of the present invention is performed, for example, according to the following procedure.
(a) Activated carbon is added to an original solution containing selenium, tellurium, and platinum group elements.
(b) Activated carbon may be separated from the soot produced by reduction by placing it in a bag of composite fiber.
(c) The liquid is heated (70 ° C. to 80 ° C.).
(d) Sulfurous acid gas or sodium sulfite is added as a reducing agent to the heated original solution to reduce the above elements.
(e) The reducing agent addition rate is adjusted while monitoring the reaction temperature. 75-80 degreeC is preferable.
(f) When the selenium concentration in the liquid becomes 3 g / L to 20 g / L, preferably 4 g / L to 18 g / L, or when the oxidation-reduction potential becomes 490 mV to 470 mV, the addition of the reducing agent is completed. The generated soot is recovered by solid-liquid separation.

In the recovery method of the present invention, the reduction of tellurium is suppressed, and the reduction of selenium, rhodium and ruthenium proceeds, so that selenium soot with a small amount of tellurium can be recovered, and rhodium soot and Ruthenium can be increased. As a result, the recovery rate of rhodium and ruthenium can be increased together with the recovery rate of selenium.

Furthermore, in the recovery method of the present invention, by adding activated carbon, the reduction of tellurium can be further suppressed and the reduction of selenium, rhodium and ruthenium can be promoted, and the recovery rate thereof can be further increased.

The graph which shows the change of the reduction | restoration state of selenium, tellurium, rhodium, and ruthenium.

Examples of the present invention are shown below. The concentrations of selenium and platinum group elements remaining in the solution after reduction were measured using ICP-AES. The amount of each element was calculated from the concentration and mass of the liquid before reduction, and the amount transferred to the soot was determined.

[Examples 1-3]
Using 500 mL of the original solution (selenium 68 g / L, tellurium 2.5 g / L, rhodium 1.5 mg / L, ruthenium 36 mg / L), warm this original solution until the liquid temperature is in the range of 70 ° C to 80 ° C. After that, sodium sulfite was added until the oxidation-reduction potential became 519 mV to 491 mV. The reaction time was adjusted by reducing the concentration of sodium sulfite. During the reaction, the amount of sodium sulfite added was adjusted so that the liquid temperature was maintained at 70-80 ° C. When the oxidation-reduction potential was reached, the addition of the reducing agent was terminated, and the generated soot was solid-liquid separated. The results are shown in Table 1.

[Examples 4 to 11]
Using the same original solution as in Examples 1 to 3, 500 mL of this original solution and 10 g of granular activated carbon in a bag were set in a container and heated until the liquid temperature reached 70 ° C., and then the oxidation-reduction potential was reduced to 507 mV to 479 mV. Sodium sulfite was added until The reaction time was adjusted by reducing the concentration of sodium sulfite. During the reaction, the amount of sodium sulfite added was adjusted so that the liquid temperature was maintained at 75 ° C. When the oxidation-reduction potential was reached, the addition of the reducing agent was terminated, and the generated soot was solid-liquid separated. The results are shown in Table 1.

In Examples 1 to 3, when the reduction was completed at an oxidation-reduction potential of 519 mV to 491 mV, the tellurium concentration remaining in the liquid was stopped at 1.9 g / L, and the selenium concentration was reduced to 9.5 to 11 g / L. The concentration can be lowered to 0.38 to 0.76 g / L and the ruthenium concentration to 19 to 25 g / L. As a result, the transfer rate of selenium to the reduced soot is 84% or more, the transfer rate of tellurium is suppressed to 27% or less, and the reduced soot containing rhodium and ruthenium can be recovered.

In Examples 4 to 11, the reduction of tellurium was achieved even when the reduction of selenium in the solution was reduced to 4.1 to 13 g / L by adding activated carbon until the redox potential was reduced to 507 mV to 473 mV. Is suppressed, and the concentration of tellurium remaining in the liquid is only 1.2 to 2.6 g / L, while the concentration of rhodium is decreased to 0.03 to 0.36 g / L and the concentration of ruthenium is decreased to 10 to 24 g / L. However, the reduction of rhodium and ruthenium proceeds, and soot rich in rhodium and ruthenium can be recovered. For example, in Examples 5 to 7 and 9 to 10, the migration rate of selenium to reduced soot is improved to 90% or more, while the migration rate of tellurium is suppressed to 37% or less except in Example 6. Moreover, the transfer rate of rhodium of Examples 4-11 is as high as 74% or more, and the transfer rate of ruthenium is also 48% or more.

Claims (6)

In a method in which a reducing agent is added to an original solution containing a platinum group element, selenium and tellurium to precipitate selenium soot, by reducing the selenium concentration in the solution from 3 g / L to 20 g / L, the reduction proceeds. A method for recovering platinum group elements and selenium, characterized by suppressing reduction and promoting reduction of selenium and platinum group elements.
The method for recovering platinum group elements and selenium according to claim 1, wherein the reduction proceeds with an oxidation-reduction potential of 520 mV to 420 mV of the original solution as an end point.
The method for recovering platinum group elements and selenium according to claim 1, wherein the reduction proceeds in the presence of activated carbon with an oxidation-reduction potential of 490 mV to 470 mV as the end point.
The method for recovering platinum group elements and selenium according to claim 3, wherein 0.03 to 0.9 times the amount of activated carbon relative to the amount of selenium in the original solution before reduction is added to the original solution to proceed the reduction.
The method for recovering a platinum group element and selenium according to any one of claims 1 to 4, wherein the reduction proceeds under heating at a liquid temperature of 70 ° C to 80 ° C.
The method for recovering a platinum group element and selenium according to any one of claims 1 to 5, wherein the liquid containing the platinum group element, selenium and tellurium is a gold extraction residue produced by a wet treatment of copper electrolytic slime.

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