JP2018162479A - Method for recovering high-purity rhenium sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing rhenium sulfide that can produce a high-purity rhenium sulfide product.SOLUTION: A method for recovering rhenium sulfide includes a leaching step 1 of subjecting an object to be treated which includes rhenium, arsenic and cadmium to oxidation leaching to produce a leachate, a neutralization solution purification step 2 of neutralizing the resultant leachate with an alkali to produce a neutralization precipitate containing arsenic and cadmium and removing the neutralization precipitate from a neutralization filtrate containing rhenium and a rhenium recovery step 3 of subjecting the neutralization filtrate to sulfuration treatment to recover rhenium contained in the neutralization filtrate as rhenium sulfide. In the rhenium recovery step 3, a washing liquid is added to the slurry before recovering rhenium sulfide and the slurry is washed under conditions of an acid concentration of 2.0 normality or less and a pH of 7.0 or less and an oxidation-reduction potential during washing in the range of -0.5 V to 0.2 V (silver/silver chloride electrode as a reference electrode).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for recovering high-purity rhenium sulfide from a sulfide containing rhenium, cadmium, arsenic and the like recovered in a non-ferrous metal smelting process.

Rhenium is a rare metal used as an additive element and catalyst for special alloys, and is naturally contained in molybdenite (MoS ₂ ), which is a raw material of molybdenum. In the smelting process of molybdenum, oxidation roasting of molybdenite is performed to solubilize molybdenum. At the time of this oxidation roasting, rhenium contained in molybdenite is separated from molybdenite as a volatile oxide Re ₂ O ₇ , recovered in a cleaning process such as a scrubber, and then purified.

In addition, it is known that pyroxenite coexists with copper minerals such as chalcopyrite (CuFeS ₂ ), but these hydropyrite and chalcopyrite are separated by a general method such as flotation. It is difficult. For this reason, when copper is obtained from chalcopyrite by dry smelting using a furnace such as a blast furnace located at the subsequent stage of flotation, pyroxenite is also charged into the furnace at the same time. As a result, volatilized rhenium is mixed in the exhaust gas mainly composed of sulfurous acid gas discharged from the furnace.

  In addition to rhenium, arsenic, cadmium, and zinc contained in copper ore float in the form of solid or liquid fine particles (also called fumes) in the exhaust gas sent to the sulfuric acid production plant as raw material gas. ing. In order to remove these impurities, the exhaust gas is subjected to a cleaning process using a scrubber or the like as a pretreatment in the sulfuric acid production process. Since rhenium contained in the exhaust gas is also separated by this cleaning process, it is necessary to selectively recover only rhenium from the above-described many types of elements.

  As one method for selectively recovering rhenium, Patent Document 1 discloses a method obtained by performing oxidative leaching on a sulfide containing at least rhenium and arsenic obtained by sulfidizing exhaust gas containing sulfurous acid gas. A method of obtaining rhenium sulfide having a low arsenic quality by separating and removing arsenic, which is an impurity, in a stable form by neutralizing the leachate with an alkali is disclosed.

  Specifically, exhaust gas containing sulfurous acid gas discharged from the smelting process of a non-ferrous metal smelting plant is washed with water in the cleaning process, and various impurity elements such as rhenium, arsenic, cadmium, etc. discharged from this cleaning process. The effluent containing sulphite is sulfurized to recover these impurity elements as sulfided starch. And it processes by this leaching process, the neutralization liquid purification process, and rhenium collection | recovery process which are shown below to collect | recover rhenium as rhenium sulfide.

(Leaching process)
In the leaching step, repulping is performed by adding a liquid containing sulfuric acid as a main component to the sulfide starch. Oxidation leaching is performed by blowing high-temperature air into the slurry obtained by repulping. Thus, a leachate having a pH of about 0 containing rhenium and some other various elements is obtained. At the same time, a leaching residue enriched with elements not leached by this oxidative leaching is obtained. The leach residue is sent to the starch treatment process where it is divided into residue and waste liquor. The divided residue is repeated in the smelting process, and the waste liquid is processed in the wastewater treatment process.

(Neutralization and purification process)
In the neutralization liquid purification step, for example, caustic soda is added to the leachate as a neutralizing agent, and neutralized at about pH 7. By filtering this, a neutralized filtrate in which rhenium is concentrated and a neutralized starch containing elements other than rhenium are obtained. This neutralized starch is repeated in the smelting process.

(Rhenium recovery process)
In the rhenium recovery step, sulfuric acid is added to the neutralized filtrate to adjust the pH to almost zero, and sodium hydrosulfide is added. The rhenium in the neutralized filtrate is precipitated as rhenium sulfide by a series of operations called sulfiding treatment consisting of filling the neutralized filtrate, adjusting the pH, and adding sodium hydrosulfide. The slurry containing rhenium sulfide is separated into solid and liquid to recover rhenium sulfide. The solution after rhenium sulfide is removed from the slurry is treated as a waste liquid in a waste water treatment step.

  Patent Document 2 discloses a method for producing rhenium sulfide having a low arsenic quality by a method comprising a leaching process, a neutralization washing process, and a rhenium recovery process similar to the above, and the cadmium quality in the rhenium sulfide is also low. A method of suppressing is disclosed. Specifically, this method is to neutralize at a higher pH by adding a calcium-based neutralizing agent after the addition of caustic soda in the neutralizing and cleaning step.

International Publication No. 2013/129130 JP-A-2015-212401

  Although rhenium sulfide having a low arsenic quality can be recovered by the methods of the above-mentioned documents 1 and 2, in any of the methods, when neutralizing the leachate containing sulfuric acid with caustic soda in the neutralization liquid cleaning step, a large amount of sodium sulfate is present. In the subsequent rhenium recovery process, it is mixed with rhenium sulfide and remains in the rhenium sulfide product as it is. Therefore, it has been required to suppress the content of sodium sulfate in rhenium sulfide to 20% by mass or less.

  As a method of keeping the sodium sulfate content low as described above, it is conceivable that the addition amount of sulfuric acid and sodium hydrosulfide in the rhenium recovery step is made lower than the specified amount. Although this method can suppress the mixing of sodium sulfate into rhenium sulfide to some extent, it sometimes causes a problem that the recovery rate of rhenium decreases. Another possible method is to wash the rhenium sulfide obtained in the rhenium recovery step with water. By this method, the content of sodium sulfate in rhenium sulfide can be made lower than the above specified value, but there is a problem that rhenium is dissolved in the cleaning liquid and the recovery rate of rhenium is lowered.

  The present invention has been made in view of the problems of the above-described conventional method for producing rhenium sulfide, and is a leaching process, a neutralization cleaning process, and a rhenium recovery process for a rhenium-containing substance such as a sulfide starch. In the method for producing rhenium sulfide, the rhenium sulfide is selectively removed by removing sodium sulfate from the slurry containing rhenium sulfide obtained by the sulfurization treatment in the rhenium recovery step. An object of the present invention is to provide a method for producing rhenium sulfide capable of producing a product.

  In order to achieve the above object, the rhenium sulfide recovery method of the present invention includes a leaching step for obtaining a leachate by oxidizing and leaching a treatment object containing rhenium, arsenic and cadmium, and neutralizing the leachate with an alkali to arsenic and cadmium. A neutralization purification step for producing a neutralized precipitate containing phosphine and removing the neutralized precipitate from the rhenium-containing neutralized filtrate, and the neutralized filtrate is subjected to sulfidation treatment and contained in the neutralized filtrate. A rhenium sulfide recovery method including a rhenium recovery step of recovering rhenium as rhenium sulfide, wherein in the rhenium recovery step, a cleaning liquid is added to the slurry before the rhenium sulfide is recovered, and the rhenium recovery step is performed at a rate of 2.0 or less. In addition, the rhenium sulfide solution is characterized by washing under conditions where the acid concentration at pH 7.0 or lower and the oxidation-reduction potential (silver-silver chloride reference electrode) are −0.5 V or higher and 0.2 V or lower. Collection method.

  According to the present invention, it is possible to reduce the concentration of impurities such as sodium sulfate in a rhenium sulfide product without substantially reducing the recovery rate of rhenium.

It is a process flowchart of the rhenium collection | recovery method of one specific example of this invention. It is the process flow figure which showed the rhenium collection | recovery process in detail among the process flows of FIG.

  Hereinafter, a specific example of the method for recovering rhenium sulfide of the present invention will be described. The method for recovering rhenium sulfide according to one embodiment of the present invention is a sulfurized starch produced by subjecting cleaning wastewater discharged when washing exhaust gas from a melting furnace of a non-ferrous metal smelting plant to sulfidation. A substance containing rhenium, arsenic and cadmium such as leaching step is obtained by oxidative leaching to obtain a leachate, and the obtained leachate is neutralized with alkali to contain arsenic and cadmium. A neutralization purification step for producing a neutralized precipitate and removing the neutralized precipitate from the neutralized filtrate containing rhenium, and a rhenium contained in the neutralized filtrate by sulfiding the resulting neutralized filtrate And a rhenium recovery step of recovering as rhenium sulfide. Hereinafter, each of these processes will be described in detail with reference to the process flow chart of FIG.

(Leaching process)
In the leaching process 1, repulping is performed by adding an aqueous solution containing sulfuric acid as a main component to the processing target such as the above-mentioned sulfided starch containing impurities such as cadmium and arsenic in addition to rhenium as an element to be recovered. High temperature air or air and water vapor are blown into the slurry produced by the repulping to perform oxidative leaching. After the oxidative leaching, solid-liquid separation is performed as necessary, so that the leaching solution having a pH of approximately 0 containing a part of most of rhenium and other various elements contained in the object to be treated, and the oxidative leaching 1 In this case, a leaching residue enriched with elements not leached is obtained. The leachate is sent to the neutralization washing step 2 described later, and the leach residue is sent to the starch treatment step 4. In the starch processing step 4, solid-liquid separation is performed by centrifugation or the like, and the residue is separated into a residue and a waste liquid. The residue is repeated in the smelting step 5 and the waste liquid is treated in the waste water treatment step 6.

(Neutralization and purification process)
In the neutralization liquid purification process 2, for example, caustic soda is added to the above leachate as a neutralizing agent and neutralized at about pH 7. After this neutralization treatment, a solid-liquid separation such as a filter press is performed to obtain a neutralized filtrate in which rhenium is concentrated and a neutralized starch composed of elements other than rhenium. After this neutralized starch is recovered, it is repeated in the smelting step 5 in the same manner as the residue in the starch processing step 4 described above.

(Rhenium recovery process)
In the rhenium recovery step 3, the neutralized filtrate obtained in the neutralization washing step 2 is subjected to sulfurization treatment, and rhenium contained in the neutralized filtrate is recovered as rhenium sulfide. The rhenium recovery step 3 will be described in more detail with reference to FIG. As shown in FIG. 2, the rhenium recovery process 3 includes a series of processes including a sulfurization process 31, a slurry washing process 32, and a solid-liquid separation process 33.

  First, at 31 in the sulfiding step, an acid and a sulfiding agent are added to the neutralized filtrate to precipitate rhenium contained in the neutralized filtrate as rhenium sulfide. In the addition of acid, the addition amount is adjusted so that the pH of the reaction solution is about 0. Although sulfuric acid or hydrochloric acid can be used as the acid to be added, it is desirable to use sulfuric acid from the viewpoint of freedom of selection of materials used for equipment such as a reaction tank and volatility.

  On the other hand, as the sulfiding agent, alkali hydrosulfide such as sodium hydrosulfide, alkali sulfide such as sodium sulfide, alkaline sulfide earth such as calcium sulfide, hydrogen sulfide, etc. can be used. Hydrogen sulfide is preferable because it is easily available, and sodium hydrosulfide is more preferable in terms of ease of handling. The suspension containing rhenium sulfide generated by this reaction is preferably a slurry containing precipitated rhenium sulfide by removing the supernatant liquid by decantation (hereinafter referred to as lower rhenium sulfide slurry or simply slurry). Is obtained.

  In the next slurry washing step 32, the above slurry is washed by adding and mixing a cleaning solution of 5 times or more on a volume basis. At that time, the acid concentration is 2.0 N or less and the pH is 7.0 or less, and the oxidation-reduction potential (measured value when a silver-silver chloride electrode is used as a reference electrode, the same applies to the subsequent oxidation-reduction potentials. The rhenium sulfide is washed under the condition of −0.5V or more and 0.2V or less. When this acid concentration exceeds 2.0 N, rhenium sulfide is redissolved. Further, even when water is added to the acidic rhenium sulfide slurry as a cleaning solution and the cleaning is repeated, the pH does not exceed 7, so the pH is set to the upper limit. When the oxidation-reduction potential exceeds 0.2 V, rhenium sulfide becomes perrhenate ions and redissolves. If a strong reducing agent is added, the oxidation-reduction potential can be lowered. However, since it is not economical, −0.5 V is sufficient as the lower limit of the oxidation-reduction potential. In addition, about the upper limit of said acid concentration, it may replace with 2.0 specification and may be limited by the pH value at the time of the said 2.0 specification. This pH value can be generally derived from pH = -log [acid concentration]. In the above case, it becomes about pH-0.3, but when the pH is less than 0, it is difficult to measure with a pH meter. Therefore, it is preferable to limit the upper limit of the acid concentration by regulation.

  In the above cleaning, if the amount of the cleaning solution is less than 5 times the volume of the slurry, the concentration of sodium sulfate contained in the cleaning solution being cleaned becomes too high, and the risk of insufficient cleaning is increased. There is a possibility that the amount carried over to the filter in the subsequent process increases with the rhenium sulfide adhesion liquid. The upper limit of the amount of the cleaning liquid is not particularly limited, but if it exceeds about 15 times, the effect is not increased any more, which is uneconomical. In order to prevent insufficient washing, it is preferable to stir for 30 minutes or more.

  The acid concentration during the washing can be adjusted within the above range by using sulfuric acid or hydrochloric acid, but sulfuric acid is used from the viewpoint of freedom of choice of materials used for equipment such as reaction vessels and volatility. It is desirable to use it. On the other hand, the redox potential can be adjusted using a reducing agent such as an alkali metal or alkaline earth metal sulfide, hydrogen sulfide, or hydrogen. Among these, since it is easily available and rhenium sulfide can be prevented from being decomposed into rhenium ions and sulfur ions, it is preferable to use sodium hydrosulfide or hydrogen sulfide, and sodium hydrosulfide is more preferable in terms of ease of handling. .

  After washing the slurry, the slurry containing the washing solution is allowed to stand for 2 hours or more for solid-liquid separation. If this standing time is shorter than 2 hours, solid-liquid separation is insufficient, and the possibility that rhenium sulfide contained in the slurry is discharged to the supernatant liquid side and becomes lost increases. In order to reduce this loss, it is conceivable to reduce the amount of the supernatant liquid to be described later. In this case, the concentration of the slurry remaining after the supernatant liquid is extracted becomes low, and the filtration time is reduced in the solid-liquid separation step 33 in the subsequent step. The production efficiency is lowered because the length becomes longer.

  Also in the standing of the slurry washing step 32, as in the case of the washing described above, the acid concentration of the slurry is 2.0 N or less, the pH is 7.0 or less, and the oxidation-reduction potential is −0.5 V or more and 0. It is preferable that the voltage be 0.2 V or less. In addition, it is preferable that the oxidation-reduction potential of the slurry does not exceed 0.2 V during the above-described cleaning or standing. As a specific method for adjusting the oxidation-reduction potential, the oxidation-reduction potential in the washing tank or the stationary tank during washing or standing is measured, and the oxidation-reduction potential is about to exceed 0.2V. Add reducing agent. Alternatively, a large amount of reducing agent is previously added to the washing water so that the redox potential does not exceed 0.2V. Further, the inside of the tank is purged with nitrogen so that oxygen in the air is not mixed into the slurry containing the cleaning liquid as much as possible.

  After standing, 80% or more of the volume of the slurry containing the cleaning liquid is extracted as a supernatant liquid. The concentrated slurry having a high rhenium sulfide concentration remaining after the removal of the supernatant liquid is then passed through a filter such as a filter press in the solid-liquid separation step 33 for filtration. After filtration of the concentrated slurry, it is preferable to pass a cleaning liquid having the same volume or more as the amount of the concentrated slurry passed through the filter through the filter. Thereby, since the filter cake is washed, the concentration of impurities such as sodium sulfate contained in rhenium sulfide can be further reduced. After washing, the filter cake is recovered from the inside of the filter and dried as necessary to obtain a rhenium sulfide product.

  In order to further increase the purity of the rhenium sulfide product, the filter cake obtained in the solid-liquid separation step 33 may be returned to the slurry washing step 32 to repeat the washing and the subsequent solid-liquid separation. In this case, the loss due to re-dissolution of rhenium can be suppressed by maintaining the acid concentration and oxidation-reduction potential of the slurry within the above range during washing and standing. By the rhenium sulfide recovery method described above, high-purity rhenium sulfide can be efficiently recovered from rhenium-containing substances such as rhenium sulfide accompanying exhaust gas discharged from a smelting furnace of a non-ferrous metal smelting plant. .

[Example 1]
The exhaust gas containing sulfurous acid gas generated at a copper smelting plant was subjected to sulfidation treatment using sodium hydrosulfide with respect to the washing effluent from the washing tower for washing with water, and the sulfurized starch containing rhenium was recovered. The sulfided starch was treated along the process flow of FIG. 1 to recover rhenium sulfide. Specifically, first, a sulfuric acid aqueous solution having a concentration of 150 g / L was added to the sulfide starch and repulped, and steam was blown in with the air so that the temperature of the resulting slurry was 70 ° C. to perform oxidative leaching. As a result, a leachate having a pH of about 0 was obtained (leaching step 1). The leachate was neutralized by adding 20% by weight of caustic soda to a pH of 6.8 at 25 ° C. to produce a neutralized starch. The neutralized starch was removed using a Nutsche with filter paper, and a neutralized filtrate was obtained (neutralization and purification step 2).

  The rhenium recovery process was performed on the neutralized filtrate according to the process flow shown in FIG. Specifically, 70% sulfuric acid was first added so that the acid concentration became 1.0N. At this time, the pH of the reaction solution was approximately zero. Next, 1.05 times the stoichiometric amount of sodium hydrosulfide required to produce rhenium sulfide from rhenium contained in the neutralized filtrate is added to carry out sulfurization treatment to produce rhenium sulfide, which is continued for 2 hours. It was allowed to stand (sulfurization step 31).

  After the elapse of 2 hours, an amount corresponding to 85% by volume of the whole was extracted from the upper portion as a supernatant. To the slurry containing the remaining rhenium sulfide, 10 times the volume of washing water was added and stirred for 40 minutes (slurry washing step 32). This washing water was prepared by using 70% sulfuric acid and sodium hydrosulfide to adjust the acid concentration to 1.0 N and a redox potential of 0.14 V using a silver-silver chloride electrode as a reference electrode. After stirring, the mixture was allowed to stand for 3 hours. During the standing, the inside of the container was purged with nitrogen to prevent oxidation by air.

  During the stirring and standing, the oxidation-reduction potential of the slurry is measured. When the oxidation-reduction potential (silver-silver chloride reference electrode) exceeds 0.15 V, a sodium hydrosulfide solution is added. Although prepared, it did not exceed 0.15V. That is, the acid concentration of the slurry during the stirring and standing was 1.0 N (pH is 0), and the oxidation-reduction potential was 0.14V.

  After standing for 3 hours, an amount corresponding to 85% of the total was taken out from the top as a supernatant, and the concentrated slurry in which the remaining rhenium sulfide was more concentrated was passed through a filter and filtered (solid-liquid separation step 33). ). In order to wash the filter cake obtained by filtration of the concentrated slurry, the washing water adjusted for the acid concentration and oxidation-reduction potential was passed through the filter by the same volume as the concentrated slurry passed through the filter. did. The filter cake was dried with a drier to produce the rhenium sulfide product of Example 1.

[Example 2]
A slurry containing rhenium sulfide was washed with wash water having a weak basicity and a high oxidation-reduction potential to produce a rhenium sulfide product of Example 2. Specifically, the neutralized filtrate is adjusted so that the acid concentration at the time of sulfuric acid addition is 2.5 N instead of 1.0 N, and the amount of sodium hydrosulfide added is the stoichiometric amount of 1. Instead of 05 times, the amount is 1.1 times, the amount of supernatant extracted to obtain a slurry containing rhenium sulfide and a concentrated slurry is changed to 80% instead of 85%, and pH 7.5 as washing water. A rhenium sulfide product of Sample 2 was prepared in the same manner as Sample 1 except that ion-exchanged water having an oxidation-reduction potential of 0.4 V was used and this was added 5 times to the slurry on a volume basis. The acid concentration of the slurry during stirring and standing was 0.5 N (pH is 0.3), and the oxidation-reduction potential was 0.11V.

[Example 3]
Using the rhenium sulfide product obtained by the method of Example 1 as a raw material, the slurry cleaning in the slurry cleaning step 32 was performed again. The conditions of Example 2 were applied as the slurry cleaning conditions. The acid concentration during stirring and standing was approximately pH 3. When the redox potential exceeded −0.07 V, sodium hydrosulfide was added to make the redox potential −0.07 V or less. The oxidation-reduction potential during standing was less than -0.07V. After standing, the slurry was filtered with a filter, and a washing liquid having the same volume as the slurry adjusted to an acid concentration pH 3 with dilute sulfuric acid and an oxidation-reduction potential of -0.07 V with sodium hydrosulfide was passed through the filter. A rhenium sulfide product of Example 3 was obtained.

[Example 4]
Using the rhenium sulfide product obtained by the method of Example 3 as a raw material, the slurry cleaning in the slurry cleaning step 32 was performed again. The conditions of Example 2 were applied as the slurry cleaning conditions. The acid concentration during stirring and standing was approximately pH 6. When the oxidation-reduction potential exceeded -0.3 V, sodium hydrosulfide was added to make the oxidation-reduction potential -0.3 V or less. The oxidation-reduction potential during standing was less than -0.3V. After allowing to stand, the slurry was filtered with a filter, and a washing solution having the same volume as the slurry adjusted to an acid concentration pH 6 with dilute sulfuric acid and an oxidation-reduction potential of -0.3 V with sodium hydrosulfide was passed through the filter. The rhenium sulfide product of Example 4 was obtained.

[Example 5]
Using the rhenium sulfide product obtained by the method of Example 1 as a raw material, the slurry cleaning in the slurry cleaning step 32 was performed again. The conditions of Example 2 were applied as the slurry cleaning conditions. The acid concentration during stirring and standing was approximately pH 3. When the oxidation-reduction potential exceeded -0.3 V, sodium hydrosulfide was added to make the oxidation-reduction potential -0.3 V or less. The oxidation-reduction potential during standing was less than -0.3V. After allowing to stand, the slurry was filtered with a filter, and a washing liquid having the same volume as the slurry adjusted to an acid concentration pH 3 with dilute sulfuric acid and an oxidation-reduction potential of -0.3 V with sodium hydrosulfide was passed through the filter. A rhenium sulfide product of Example 5 was obtained.

[Comparative Example 1]
A slurry containing rhenium sulfide was produced in the same manner as in Example 1 until the sulfiding step 31, and after standing for 2 hours, an amount corresponding to 85% by volume of the whole was extracted from the top as a supernatant, and the remaining rhenium sulfide was obtained. A cleaning solution having an acid concentration of 1 N with 10 times the volume of dilute sulfuric acid was added to the slurry containing and stirred for 40 minutes. The acid concentration during stirring was 1.0N. The redox potential was not adjusted during stirring and standing. Therefore, the oxidation-reduction potential was initially 0.16V, but gradually oxidized and the oxidation-reduction potential became 0.4V at the end of stirring. After stirring, the mixture was allowed to stand for 3 hours. The nitrogen purge inside the container was not performed during stirring and standing.

  After standing for 3 hours, an amount corresponding to 85% of the whole was taken out from the upper portion as a supernatant, and the remaining concentrated slurry in which rhenium sulfide was further concentrated was passed through a filter and filtered. In order to wash the obtained filter cake, a washing liquid prepared with dilute sulfuric acid to an acid concentration of 1.0 N was passed through the filter by the same volume as the concentrated slurry passed through the filter. The oxidation-reduction potential of the cleaning liquid was 0.4V. The filter cake was dried with a drier to produce a rhenium sulfide product of Comparative Example 1.

[Comparative Example 2]
After producing the slurry containing rhenium sulfide in the same manner as in Example 2 up to the sulfiding step 31, the same amount of ion-exchanged water as in Example 2 was added in the slurry washing step 32, replacing the 40 minutes. And stirred for 1 hour. Thereafter, it was allowed to stand for 3 hours. The acid concentration during stirring was approximately pH 3. The redox potential was not adjusted during stirring and standing. Therefore, the oxidation-reduction potential was initially 0.01 V. However, the oxidation-reduction potential became 0.4 V at the end of stirring by gradually participating. After stirring, the mixture was allowed to stand for 3 hours. The nitrogen purge inside the container was not performed during stirring and standing.

  After standing, the slurry was filtered with a filter, and a cleaning liquid having the same volume as the slurry adjusted to an acid concentration pH 3 with diluted sulfuric acid was passed through the filter to obtain a rhenium sulfide product of Comparative Example 2. The oxidation-reduction potential of the cleaning liquid was 0.4V. The filter cake was dried with a drier to produce a rhenium sulfide product of Comparative Example 2.

[Comparative Example 3]
A slurry containing rhenium sulfide was produced in the same manner as in Example 1 up to the sulfidation step 31, and then the slurry was directly passed through a filter in a solid-liquid separation step 33 without being treated in the slurry washing step 32, and sulfided. A rhenium filter cake was obtained. The filter cake was dried with a drier to produce a rhenium sulfide product of Comparative Example 3.

When producing rhenium sulfide in Examples 1 to 5 and Comparative Examples 1 to 3, ICP analysis was performed on the content of rhenium contained in the supernatant liquid (except in the case of Comparative Example 3), filtrate and rhenium sulfide product after washing. Rhenium quality and rhenium recovery were obtained by measuring with an apparatus. At that time, all the rhenium sulfide in the rhenium sulfide product was converted as dirhenium heptasulfide (VII) (Re ₂ S ₇ ). The rhenium sulfide ratio and sodium sulfide ratio were determined from the mass of the rhenium sulfide product, the mass of dirhenium heptasulfide in the rhenium sulfide product, and the mass of sodium sulfide. The rhenium quality, rhenium sulfide ratio and recovery rate of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 below.

  From the results of Table 1 above, in Examples 1 to 5 in which rhenium sulfide was washed under the conditions satisfying the requirements of the present invention, rhenium sulfide products having high rhenium quality could be recovered at a high recovery rate. On the other hand, in Comparative Examples 1 and 2 in which rhenium sulfide was cleaned but the redox potential was not adjusted, the rhenium quality of the rhenium sulfide product was high, but the recovery rate was poor. In Comparative Example 3, rhenium sulfide was not washed, so the rhenium recovery rate was high, but the rhenium quality in the rhenium sulfide product was low.

DESCRIPTION OF SYMBOLS 1 Leaching process 2 Neutralization liquid purification process 3 Rhenium collection process 31 Sulfurization process 32 Slurry washing process 33 Solid-liquid separation process

Claims (4)

A leaching process for obtaining a leachate by oxidizing and leaching a treatment object containing rhenium, arsenic and cadmium, and neutralizing the leachate with an alkali to produce a neutralized precipitate containing arsenic and cadmium, and containing rhenium A rhenium sulfide process comprising: a neutralization purification process for removing the neutralized precipitate from the sum filtrate; and a rhenium recovery process for sulfiding the neutralized filtrate to recover rhenium contained in the neutralized filtrate as rhenium sulfide. A collection method,
In the rhenium recovery step, before the rhenium sulfide is recovered, a washing solution is added to the slurry, so that an acid concentration of 2.0 N or less and pH 7.0 or less, and a redox potential (silver-silver chloride reference electrode) are obtained. -A method for recovering rhenium sulfide, comprising washing under conditions of 0.5 V or more and 0.2 V or less.   In the rhenium recovery step, decantation is performed after the sulfurization treatment, and after the supernatant liquid is removed, the cleaning liquid is added to the slurry containing rhenium sulfide, and the mixture is stirred under the conditions of the acid concentration and the oxidation-reduction potential. 2. The method for recovering rhenium sulfide according to claim 1, wherein the cleaning is performed by standing.   The slurry containing rhenium sulfide after being washed with the washing liquid is passed through a filter and filtered, and then washed by passing the washing liquid having the acid concentration and oxidation-reduction potential through the filter cake in the filter. The method for recovering rhenium sulfide according to claim 2, wherein: The raw material containing the rhenium, arsenic, and cadmium is recovered from a cleaning effluent discharged from a cleaning process of washing exhaust gas containing sulfurous acid gas generated from a non-ferrous metal smelting plant. The manufacturing method of rhenium sulfide of any one of 1-3.

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