JP2018115380A - Method for separating tellurium and platinum group metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a platinum group metal together with tellurium that prevents shortening of the lifetime of an extraction solvent and efficiently separates tellurium and a platinum group metal.SOLUTION: The method for separating tellurium and a platinum group metal comprises: a step of adjusting a chloride ion concentration in an aqueous solution containing tellurium and a platinum group metal (hereinafter referred to as a treating solution) to not less than 3 mol/L to less than 5 mol/L; a step of mixing the treating solution having a chloride ion concentration adjusted to the above-mentioned range into a dibutyl carbitol liquid as an organic solvent to extract tellurium of the treating solution in the organic solvent; a hydrochloric acid washing step of separating and taking out an organic phase including tellurium and a water phase in which a platinum group metal remains, washing the organic phase using hydrochloric acid having a concentration of not less than 4 mol/L to less than 5 mol/L to migrate the platinum group metal to the hydrochloric acid, mixing hydrochloric acid as a post-washing liquid into the water phase separated from a tellurium extraction step; a step of mixing the organic phase subjected to hydrochloric acid washing into water or hydrochloric acid having a concentration of 2 mol/L or less to back-extract tellurium in the hydrochloric acid; and a step of separating and taking out the water phase in which tellurium is back-extracted from the organic phase.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for efficiently separating tellurium and platinum group elements from hydrochloric acid leaching of copper electrolytic slime.

  In the copper electrolysis process in the copper smelting process, copper electrolysis slime is generated as a by-product. This copper electrolytic slime contains a trace amount of noble metals such as gold, silver and platinum group elements together with copper, and is used as a noble metal recovery raw material. For example, after the copper electrolytic slime is decopperized, gold, platinum group elements, selenium, tellurium, and the like are leached by chlorination and leaching, and gold is extracted from the leaching solution by solvent extraction. A method is known in which gas is blown and selenium, tellurium, and a platinum group element are recovered as a reducing soot, and selenium is distilled and separated from the reducing soot to recover a distillation residue containing tellurium and the platinum group element.

  Also known is a treatment method for separating the platinum group element from the solution after gold extraction by solvent extraction. For example, the platinum group element is extracted by contacting trioctylmethylammonium chloride and tributyl phosphate with the solution after gold extraction. Later, a method of reducing and recovering selenium and tellurium by blowing sulfurous acid gas into this extraction residual liquid is described (Patent Document 1: Japanese Patent Application Laid-Open No. 2001-207223). In addition, as a method for recovering a platinum group element from a solution containing a platinum group element, a solvent extraction method using dialkyl sulfide (DAS) or tributyl phosphoric acid (TBP) is known (Patent Document 2: Japanese Patent Application Laid-Open No. 2000-200012). -178664).

  Furthermore, as a method for extracting tellurium from a solution containing tellurium and a platinum group element, tetravalent tellurium ions and 5 to 9 mol / L chloride ions are contained, and 3 mol / L or more of the chloride ions is hydrochloric acid. The aqueous solution in the form is mixed with dibutyl carbitol as an extraction solvent, the tellurium is selectively extracted, the organic phase from which the tellurium has been extracted is washed with 5 to 9 mol / L hydrochloric acid, and then the platinum group element is washed away. A method is known in which tellurium is back-extracted and reduced to recover metal tellurium (Patent Document 3: JP 2000-239753).

JP 2001-207223 A JP 2000-178664 A JP 2000-239753

  In the method of Patent Document 3, in the solvent extraction using dibutyl carbitol, the chloride ion concentration of the solution is adjusted to 5 to 9 mol / L (hydrochloric acid concentration) in order to increase the extraction rate of tellurium contained in the hydrochloric acid leaching solution. 3mol / L or more). Specifically, Table 2 of Patent Document 3 shows that while the stock solution 1 (chlorine concentration 4 g / l, hydrochloric acid concentration 2.9 g / l), the tellurium concentration of the organic phase is 0.01 g / l, For stock solution 2 (chlorine concentration 7 g / l, hydrochloric acid concentration 6.6 g / l), the tellurium concentration of the organic phase is 5.8 g / l, and the extraction rate of tellurium varies greatly depending on the chloride ion concentration and hydrochloric acid concentration. It is shown.

  However, since the method of Patent Document 3 has a high chloride ion concentration or hydrochloric acid concentration in the tellurium extraction step and organic phase washing step, the separation between the organic phase and the aqueous phase (referred to as phase separation) is inferior. There is a problem that the extraction rate of tellurium is lowered, and a part of the platinum group element in the aqueous phase is transferred to the organic phase, so that the loss of the platinum group element contained in the aqueous phase is increased.

  The present invention solves the above-mentioned problems in tellurium solvent extraction, and in the tellurium extraction step and the organic phase hydrochloric acid washing step, the chloride ion concentration or the hydrochloric acid concentration is set within a range in which the organic phase and the aqueous phase are well separated. Provided is a method for efficiently separating tellurium and platinum group elements by setting and maintaining a high extraction ratio of tellurium and reducing loss of platinum group elements contained in an aqueous phase.

The present invention relates to the following processing methods.
[1] A method for separating tellurium and a platinum group element, comprising the following steps (a) to (e):
(A) adjusting the chloride ion concentration of an aqueous solution containing tellurium and a platinum group element (referred to as a treatment solution) to 3 mol / L or more and less than 5 mol / L;
(B) a step of mixing a treatment solution adjusted in chloride ion concentration with a dibutyl carbitol solution of an organic solvent to extract tellurium in the treatment solution into an organic phase of the organic solvent;
(C) The organic phase containing tellurium and the aqueous phase in which the platinum group element remains are separated and removed, and the organic phase is washed with hydrochloric acid having a concentration of 4 mol / L to less than 5 mol / L, and the organic phase A hydrochloric acid washing step of transferring the platinum group element in the hydrochloric acid, and mixing the hydrochloric acid in the solution after washing into the aqueous phase separated from the tellurium extraction step,
(D) A step of mixing the organic phase washed with hydrochloric acid with water or hydrochloric acid having a concentration of 2 mol / L or less and back-extracting tellurium into the hydrochloric acid.
(E) A step of separating and taking out the aqueous phase from which the tellurium has been back-extracted from the organic phase.
[2] The separation method according to [1], wherein the treatment solution containing tellurium and a platinum group element is a hydrochloric acid leaching solution of copper electrolytic slime.
[3] The separation method according to [1] or [2] above, wherein the aqueous phase separated from the tellurium extraction step is mixed with the solution after washing in the hydrochloric acid washing step and used for recovery of the platinum group element.

[Specific method]
The treatment method of the present invention is a method for separating tellurium and a platinum group element, which comprises the following steps (a) to (e).
(A) adjusting the chloride ion concentration of an aqueous solution (treatment solution) containing tellurium and a platinum group element to 3 mol / L or more and less than 5 mol / L;
(B) a step of mixing a treatment solution adjusted in chloride ion concentration with a dibutyl carbitol solution of an organic solvent to extract tellurium in the treatment solution into an organic phase of the organic solvent;
(C) The organic phase containing tellurium and the aqueous phase in which the platinum group element remains are separated and removed, and the organic phase is washed with hydrochloric acid having a concentration of 4 mol / L to less than 5 mol / L, and the organic phase A hydrochloric acid washing step of transferring the platinum group element in the hydrochloric acid, and mixing the hydrochloric acid in the solution after washing into the aqueous phase separated from the tellurium extraction step,
(D) A step of mixing the organic phase washed with hydrochloric acid with water or hydrochloric acid having a concentration of 2 mol / L or less and back-extracting tellurium into the hydrochloric acid.
(E) A step of separating and taking out the aqueous phase from which the tellurium has been back-extracted from the organic phase.

  An outline of the treatment method of the present invention is shown in FIG. In the figure, organic phase I is the organic phase prior to hydrochloric acid washing after extraction of tellurium, organic phase II is the organic phase in the hydrochloric acid washing process, organic phase III is the organic phase in the back extraction process, and organic phase IV is after the back extraction. Organic phase.

  In the treatment method of the present invention, a hydrochloric acid leaching solution of copper electrolytic slime can be used as the solution containing tellurium and a platinum group element. For example, gold is extracted from a hydrochloric acid leaching solution of copper electrolysis slime by solvent extraction, and then sulfur dioxide gas is blown into the solution after gold extraction, selenium, tellurium and platinum group elements are reduced into a reducing soot, and selenium is distilled and separated from the reducing soot. The remaining hydrochloric acid treatment solution or the like can be used.

[Chloride ion concentration adjustment process]
A hydrochloric acid leaching solution containing tellurium and a platinum group element is used as a treatment solution, and the chloride ion concentration of the treatment solution is adjusted to 3 mol / L or more and less than 5 mol / L. When dibutyl carbitol (DBC) is used as an organic solvent for extracting tellurium, tellurium is not sufficiently extracted into the organic phase at a chloride ion concentration of less than 3 mol / L. On the other hand, when the chloride ion concentration is 5 mol / L or more, the phase separation between the organic phase and the aqueous phase decreases, so that part of the platinum group elements contained in the aqueous phase are taken into the organic phase and recovered from the aqueous phase. Element loss increases. Further, when the chloride ion concentration is 7 mol / L or more, the phase separation between the organic phase and the aqueous phase is further lowered, and it is difficult to separate and recover the aqueous phase (Example 1, Table 1, treatment solution E). Further, when the chloride ion concentration becomes high, the corrosion of the apparatus becomes severe, which is not industrially practical.

  In hydrochloric acid leaching solution of copper electrolytic slime, about 50% to about 90% of chloride ions are hydrochloric acid. When the chloride ion concentration is lower than the above range, hydrochloric acid is added, and when the chloride ion concentration is higher than the above range, The solution may be diluted to adjust the chloride ion concentration to the above range.

[Tellurium extraction process]
Hydrochloric acid leaching solution with adjusted chloride ion concentration is used as a treatment solution, and organic solvent is mixed to extract tellurium into the organic phase. As the organic solvent, dibutyl carbitol solution (DBC) is preferably used. The organic solvent (O) and the treatment solution (aqueous phase: A) are mixed, for example, in a liquid amount of O / A = 1: 1, shaken for 10 minutes, and then allowed to stand for 30 minutes. The two phases may be separated. The tellurium of the treatment solution is extracted into the organic phase. On the other hand, when the chloride ion concentration is in the above range, most of the platinum group elements remain in the aqueous phase without being extracted into the organic phase. The organic phase and the aqueous phase are separated and removed.

[Hydrochloric acid washing process]
Since the organic phase from which the tellurium has been extracted contains a part of the platinum group element, the organic phase is washed with hydrochloric acid, and the platinum group element in the organic phase is transferred to hydrochloric acid. Since the hydrochloric acid in the liquid after washing contains a platinum group element, the liquid after washing is mixed with the aqueous phase separated from the tellurium extraction step, and the platinum group element is recovered from this mixed liquid.

  The concentration of hydrochloric acid used for washing the organic phase is preferably 4 mol / L or more and less than 5 mol / L. When the hydrochloric acid concentration is 5 mol / L or more, the phase separation between the organic phase and the aqueous phase is lowered, so that it is difficult to sufficiently transfer the platinum group element in the organic phase to the aqueous phase. Further, if the hydrochloric acid concentration is less than 4 mol / L, the ratio of tellurium in the organic phase to be back-extracted into hydrochloric acid increases, which is not preferable. For washing the organic phase with hydrochloric acid, for example, the mixture is mixed in a liquid amount of O / A = 0.4, shaken for 10 minutes, and allowed to stand for 30 minutes to separate the aqueous phase. This operation may be repeated several times.

[Back extraction process]
The organic phase washed with hydrochloric acid is mixed with water or dilute hydrochloric acid having a concentration of 2 mol / L or less, and tellurium is back-extracted into the aqueous phase. When the hydrochloric acid concentration is higher than 2 mol / L, tellurium is not sufficiently back-extracted. Tellurium is recovered from the aqueous phase containing back-extracted tellurium. In this back extraction, for example, the mixture is mixed in a liquid amount of O / A = 0.4, shaken for 10 minutes, and then left to stand for 30 minutes to separate the aqueous phase. This operation may be repeated several times.

[Tellurium recovery process]
For example, when sulfurous acid gas is passed through an aqueous phase containing tellurium, tellurium-containing precipitates are formed, so that metal tellurium can be obtained by redissolving the precipitates and reducing again after impurity separation.
Alternatively, when caustic soda is added to the aqueous phase containing tellurium and neutralized, precipitation of tellurium dioxide occurs, and metal tellurium can be obtained by recovering and reducing the tellurium dioxide.

[Platinum group element recovery process]
The solution after washing in the hydrochloric acid washing step is mixed with the aqueous phase separated from the tellurium extraction step, and the platinum group element is recovered from this mixture. Specifically, the chloride ion concentration in the aqueous phase separated from the tellurium extraction step is 3 mol / L or more and less than 5 mol / L, and the hydrochloric acid concentration in the solution after hydrochloric acid washing is 4 mol / L or more and less than 5 mol / L. Therefore, most of the platinum group elements contained in the mixed solution form a chloride complex. When an ammonium chloride solution is added to this mixture, platinum forms ammonium chloroplatinate and selectively precipitates. Therefore, the precipitate can be filtered and heated to 800 ° C. to 950 ° C. to recover metallic platinum. it can.

  When aqueous ammonia is added to the filtrate from which platinum has been precipitated and separated, dichloroamine palladium precipitates. By collecting this precipitate and heat-treating it, metallic palladium can be obtained. When an oxidizing agent such as sodium bromate is added to the solution from which palladium is separated and heated at 60 to 80 ° C., ruthenium tetroxide gas is generated, and it is recovered in the form of sodium ruthenate by absorbing it in hydrochloric acid. be able to. The residual liquid from which ruthenium is recovered contains rhodium, but sodium nitrite is added to the residual liquid to nitrite rhodium, and then ammonium chloride is added to recover rhodium in the form of rhodium nitrate. it can.

  By adding hydrazine or the like to the organic phase after back-extracting the tellurium and reducing it, residual metals such as gold remaining in the organic phase can be precipitated and recovered.

  According to the treatment method of the present invention, the separation effect of tellurium and platinum group elements can be enhanced. Specifically, for example, palladium, ruthenium, and rhodium can recover platinum group elements with a transfer rate of 100% and platinum with a transfer rate of 99.7%, while tellurium can recover tellurium with a transfer rate of 70% or more. Tellurium and platinum group elements are well separated.

  In the treatment method of the present invention, in the tellurium extraction step, the chloride ion concentration of the treatment solution is 3 mol / L or more to less than 5 mol / L, and the hydrochloric acid concentration in the hydrochloric acid washing step is 4 mol / L or more to less than 5 mol / L. Therefore, the concentration of hydrochloric acid is lower than that of the conventional treatment method, the phase separation between the organic phase and the aqueous phase is good, and the loss of platinum group elements taken into the organic phase is reduced.

  Since the concentration of hydrochloric acid used for back extraction is 2 mol / L or less, the environmental load can be reduced in the drainage treatment after tellurium recovery. Moreover, since the processing method of this invention can perform each processing process at about room temperature, it can reduce energy cost.

Process drawing which shows the outline of the process of this invention.

  Hereinafter, embodiments of the present invention will be described. The concentrations of tellurium and platinum group elements were measured by ICP-AES.

[Example 1] Concentrated hydrochloric acid is added to the copper electrolytic slime solution of the tellurium extraction source solution to obtain chloride ion concentrations shown in Table 1, and hydrogen peroxide is added dropwise while maintaining the solution temperature at 60 to 70 ° C. Oxidation leaching was performed to obtain treatment solutions A to E. Table 1 shows the contents of tellurium and platinum group elements in the original solution. Table 1 shows the chloride ion concentrations of the treatment solutions A to E.
The treatment solutions A to E were mixed with dibutyl carbitol (DBC) in a liquid amount of O / A = 1: 1, shaken for 10 minutes, allowed to stand for 30 minutes, and separated into two layers. And obtained an aqueous phase. The results are shown in Table 1. The extraction rate was calculated according to the following formula [1].
Extraction rate% = quantity in organic phase / quantity in treatment solution × 100 [1]

  As shown in Table 1, the treatment solutions A to C having a chloride ion concentration within the range of the present invention have a high extraction rate of tellurium into the organic phase, but the treatment solution D having a chloride ion concentration of 2.0 mol / L is In the case of the treatment solution E having a low tellurium extraction rate and a chloride ion concentration of 7.0 mol / L, it is difficult to separate the organic phase and the aqueous phase. In addition, the numerical value of the organic phase of the process solution E is a measured value of the part in which an aqueous phase is not mixed.

[Example 2] Hydrochloric acid washing About the tellurium-extracted organic phase of treatment solution B in Table 1, hydrochloric acid having a concentration shown in Table 2 was mixed in a liquid amount of O / A = 0.4 and shaken for 10 minutes. The aqueous phase was separated by standing for 30 minutes. This operation was repeated 4 times for a total of 5 times of hydrochloric acid washing, and the aqueous phases after each washing were combined to obtain post-washing solutions B1 to B4. The concentrations of tellurium and platinum group elements contained in the post-cleaning solutions B1 to B4 were quantified, and the cleaning rate was calculated. The cleaning rate was calculated by the following formula [2]. The results are shown in Table 2.
Washing rate% = quantity in liquid after washing / quantity in organic phase before washing × 100 (2)

  As shown in Table 2, in washing with hydrochloric acid having a hydrochloric acid concentration of 4 mol / L or more and less than 5 mol / L, most of the platinum group elements mixed in the organic phase were washed and transferred to the hydrochloric acid after washing. . The cleaning rate is 94% or more. The washing rate of tellurium is 17% or less, and platinum group elements are selectively washed while suppressing elution of tellurium (after-washing solutions B1 and B2). On the other hand, in washing with hydrochloric acid having a hydrochloric acid concentration of 3 mol / L, the amount of tellurium transferred from the organic phase to hydrochloric acid increases (liquid B3 after washing), and in washing with hydrochloric acid having a hydrochloric acid concentration of 7 mol / L, the organic phase. It was difficult to separate the water phase and the water phase could not be recovered. (After-washing liquid B4).

[Example 3] Tellurium back-extraction The organic phase subjected to hydrochloric acid washing of the post-washing liquid B1 shown in Table 2 was mixed with hydrochloric acid having a concentration shown in Table 3 at a liquid volume of O / A = 0.4, After shaking for 10 minutes, the mixture was allowed to stand for 30 minutes to separate the aqueous phase. This operation was further repeated 4 times for a total of 5 back extractions to obtain back extracts O to R. The amounts of tellurium and platinum group elements contained in the back extracts O to R were quantified, and the back extraction rate was calculated based on the following formula [3]. Moreover, the transfer rate was calculated | required based on following Formula [4]. These results are shown in Table 3.

As shown in Table 3, the total amount of tellurium and platinum group elements was back-extracted from the back extracts O to Q using hydrochloric acid having a concentration of 0 to 2 mol / L. On the other hand, the back extraction rate of the back extract R using 3 mol / L hydrochloric acid is 55%, and the back extraction of tellurium is difficult to proceed.
Reverse extraction rate% = quantity in the back extract / quantity in the organic phase II before back extraction x 100 ... [3]
Migration rate% = quantity in back extract / quantity in original liquid (copper electrolytic slime solution) × 100 (4)

  According to the treatment method of the present invention, as shown in Table 1, 75.8% to 91% of tellurium contained in the treatment solution is extracted into the organic phase, and the whole amount of palladium is extracted into the organic phase. The extraction rate of platinum group elements other than palladium is several percent (treatment solutions A to C). Next, as shown in Table 2, the platinum group elements contained in the organic phase are washed with hydrochloric acid to wash the whole amount of palladium, ruthenium and rhodium, and platinum is washed and separated from the organic phase by 94% or more ( Post-cleaning liquids B1, B2). On the other hand, the washing rate of tellurium is 14% to 17%, and most of the tellurium remains in the organic phase.

In the back extraction of the organic phase washed with hydrochloric acid, as shown in Table 3, according to the treatment method of the present invention, 74% of tellurium contained in the organic phase is back extracted. On the other hand, the organic phase washed with hydrochloric acid does not contain palladium, ruthenium, or rhodium at all, and the amount of platinum in the organic phase is very small. Therefore, the back extract does not contain any palladium, ruthenium, or rhodium, and the platinum in the back extract is very small, and the separation effect of tellurium and the platinum group element is good when the back extraction process is performed. Furthermore, in the treatment method of the present invention, palladium, ruthenium, and rhodium are not contained in the organic phase or the back extract at all, and platinum is a very small amount, so that there is almost no loss of the platinum group element (back extract O ~ Q).

Claims (3)

A method for separating tellurium and a platinum group element, comprising the following steps (a) to (e):
(A) adjusting the chloride ion concentration of an aqueous solution containing tellurium and a platinum group element (referred to as a treatment solution) to 3 mol / L or more and less than 5 mol / L;
(B) a step of mixing a treatment solution adjusted in chloride ion concentration with a dibutyl carbitol solution of an organic solvent to extract tellurium in the treatment solution into an organic phase of the organic solvent;
(C) The organic phase containing tellurium and the aqueous phase in which the platinum group element remains are separated and removed, and the organic phase is washed with hydrochloric acid having a concentration of 4 mol / L to less than 5 mol / L, and the organic phase A hydrochloric acid washing step of transferring the platinum group element in the hydrochloric acid, and mixing the hydrochloric acid in the solution after washing into the aqueous phase separated from the tellurium extraction step,
(D) A step of mixing the organic phase washed with hydrochloric acid with water or hydrochloric acid having a concentration of 2 mol / L or less and back-extracting tellurium into the hydrochloric acid.
(E) A step of separating and taking out the aqueous phase from which the tellurium has been back-extracted from the organic phase. The separation method according to claim 1, wherein the treatment solution containing tellurium and a platinum group element is a hydrochloric acid leaching solution of copper electrolytic slime. The separation method according to claim 1 or 2, wherein the aqueous phase separated from the tellurium extraction step is mixed with the solution after washing in the hydrochloric acid washing step and used for recovery of the platinum group element.

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