JP6842041B2 - How to recover high-purity rhenium sulfide - Google Patents

Description

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

Rhenium is a rare metal used as an additive element for special alloys and catalysts, and is naturally contained in _{molybdenite (MoS 2), which is mainly a raw material for molybdenum.} In the molybdenum smelting process, molybdenite is oxidatively roasted in order to make molybdenum soluble. During this oxidative roasting, rhenium contained in molybdenite is _{separated from molybdenite as volatile oxide Re 2} O ₇ , recovered in a washing step of scrubber and the like, and then refined.

Molybdenite is known to coexist with copper minerals such as chalcopyrite (CuFeS ₂ ), but these molybdenite and chalcopyrite are separated by a general method such as flotation. Is difficult. Therefore, when copper is obtained from chalcopyrite by pyrometallurgy using a furnace such as a blast furnace located after the flotation, molybdenite 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 the above-mentioned renium, arsenic, cadmium, zinc, etc. contained in copper ore are suspended in the form of solid or liquid fine particles (also called fumes) in this exhaust gas sent to the sulfuric acid production plant as a raw material gas. ing. In order to remove these impurities, the exhaust gas is cleaned with a scrubber or the like as a pretreatment for the sulfuric acid production process. Since rhenium contained in the exhaust gas is also separated by this cleaning treatment, it is necessary to selectively recover only rhenium from the above-mentioned many kinds of elements.

As one of the methods for selectively recovering rhenium, Patent Document 1 describes oxidative leaching of sulfide containing at least rhenium and arsenic obtained by sulfurizing an exhaust gas containing sulfurous acid gas. A method has been disclosed in which arsenic, which is an impurity, is separated and removed in a stable form by neutralizing the leachate with alkali to obtain rhenium sulfide having a low arsenic grade.

Specifically, the exhaust gas containing sulfurous acid gas discharged from the smelting process of a non-ferrous metal smelting factory is washed with water in the cleaning process, and various impurity elements such as renium, arsenic, and cadmium discharged from this cleaning process are washed. The washing effluent containing the above is smelted to recover these impurity elements as sulfide starch. Then, the sulfide starch is treated in the leaching step, the neutralizing liquid purification step, and the rhenium recovery step shown below to recover rhenium as rhenium sulfide.

(Leaching process)
In the leaching step, a liquid containing sulfuric acid as a main component is added to the sulfide starch to repulp. Oxidative leaching is performed by blowing high-temperature air into the slurry obtained by repulp. This gives a leachate with a pH of approximately 0 containing rhenium and some of the other various elements. At the same time, an leaching residue is obtained in which the elements that were not leached by this oxidative leaching are concentrated. The leaching residue is sent to a starch treatment step where it is separated into a residue and a effluent. The separated residue is repeated in the melting step, and the waste liquid is treated in the wastewater treatment step.

(Neutralization purification process)
In the neutralization purification step, for example, caustic soda is added as a neutralizing agent to the leachate, and the neutralization treatment is performed at about pH 7. By filtering this, a neutralized filtrate containing concentrated rhenium and a neutralized starch containing an element other than rhenium can be obtained. This neutralized starch is repeated in the melting process.

(Rhenium recovery process)
In the rhenium recovery step, sulfuric acid is added to the neutralization filtrate to adjust the pH to almost 0, and sodium hydrosulfide is added. Rhenium in the neutralization filtrate is precipitated as rhenium sulfide by a series of operations called sulfurization treatment consisting of liquid filling of the neutralization filtrate, pH adjustment, and addition of sodium hydrosulfide. The slurry containing rhenium sulfide is solid-liquid separated to recover rhenium sulfide. After the rhenium sulfide is removed from the slurry, the solution is treated as a waste liquid in the wastewater treatment step.

Further, in Patent Document 2, in a method for producing rhenium sulfide having a low arsenic grade by a method consisting of a leaching step, a neutralizing cleaning step, and a rhenium recovery step similar to the above, the cadmium grade in the rhenium sulfide is also low at the same time. A method of suppressing it is disclosed. Specifically, in this method, in the neutralization purification step, a calcium-based neutralizer is added after the addition of caustic soda to neutralize at a higher pH.

International Publication No. 2013/129130 Japanese Unexamined Patent Publication No. 2015-212401

Although rhenium sulfide having a low arsenic grade can be recovered by the methods of Documents 1 and 2 above, in any of the methods, when the leachate containing sulfuric acid is neutralized with caustic soda in the neutralization purification step, a large amount of sodium sulfate is contained. In the rhenium recovery step of the subsequent step, it is mixed with rhenium sulfide and remains in the rhenium sulfide product as it is, which may cause a problem. 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 suppressing the sodium sulfate content to a low level as described above, it is conceivable to reduce the amount of sulfuric acid and sodium hydrosulfide added in the rhenium recovery step to a value lower than the specified amount. Although this method can suppress the mixing of sodium sulfate into rhenium sulfide to some extent, it may cause a problem that the recovery rate of rhenium is lowered. Further, as another method, it is conceivable 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-mentioned 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-mentioned conventional method for producing rhenium sulfide, and is a rhenium-containing substance such as sulfide starch, a leaching step, a neutralizing cleaning step, and a rhenium recovery step. In the method for producing rhenium sulfide to produce rhenium sulfide by treating it in a series of steps consisting of, sodium sulfate is selectively removed from the slurry containing rhenium sulfide obtained by the rhenium disulfide treatment in the rhenium recovery step to obtain high-purity rhenium sulfide. It is an object of the present invention to provide a method for producing rhenium sulfide capable of producing a product.

In order to achieve the above object, the method for recovering rhenium sulfide of the present invention includes a leaching step of oxidatively leaching an object to be treated containing renium, arsenic and cadmium to obtain a leachate, and neutralizing the leachate with alkali to neutralize arsenic and cadmium. A neutralization purification step of producing a neutralized precipitate containing the above-mentioned material and removing the neutralized precipitate from the neutralized filtrate containing renium, and a sulfurization treatment of the neutralized filtrate to be contained in the neutralized filtrate. A method for recovering rhenium sulfide, which comprises a renium recovery step of recovering renium as renium sulfide. In the renium recovery step, a cleaning liquid is added to the slurry before the renium sulfide is recovered, and the value is 2.0 or less. A method for recovering rhenium sulfide, which comprises washing under conditions of an acid concentration of pH 7.0 or less and an oxidation-reduction potential (silver-silver chloride reference electrode) of −0.5 V or more and 0.2 V or less.

According to the present invention, the concentration of impurities such as sodium sulfate in rhenium sulfide products can be reduced without reducing the recovery rate of rhenium.

It is a process flow chart of the rhenium recovery method of one specific example of this invention. It is a process flow diagram which showed the rhenium recovery process in detail in the process flow 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, which is a specific example of the present invention, is a sulfurized starch produced by subjecting the washing wastewater discharged when the exhaust gas from the smelting furnace of a non-ferrous metal smelting plant is washed with water to sulfurization treatment. Substances containing rhenium, arsenic, and cadmium, such as, are treated as objects to be treated, and the leaching step of oxidatively leaching this object to obtain a leachate and neutralizing the obtained leachate with alkali to contain arsenic and cadmium. A neutralizing solution step of producing a neutralizing precipitate and removing the neutralizing precipitate from the neutralizing filtrate containing renium, and sulfurizing the obtained neutralizing filtrate to contain renium contained in the neutralizing filtrate. Consists of a renium recovery step of recovering as renium sulfide. Hereinafter, each of these steps will be specifically described with reference to the process flow chart of FIG.

(Leaching process)
In the leaching step 1, in addition to rhenium, which is an element to be recovered, an aqueous solution containing sulfuric acid as a main component is added to a treatment target such as the above-mentioned sulfide starch containing impurities such as cadmium and arsenic to repulp. High temperature air or air and water vapor are blown into the slurry produced by this repulp to perform oxidative leaching. After oxidative leaching, solid-liquid separation is performed as necessary to obtain a leachate having a pH of about 0 containing most of rhenium and some other various elements contained in the object to be treated, and the oxidative leaching 1 Then, an leaching residue in which the elements that have not been leached is concentrated is obtained. The leaching solution is sent to the neutralization washing step 2 described later, and the leaching residue is sent to the starch treatment step 4. In this starch treatment step 4, solid-liquid separation is performed by centrifugation or the like, and the residue and waste liquid are separated. The residue is repeated in the melting step 5, and the waste liquid is treated in the wastewater treatment step 6.

(Neutralization purification process)
In the neutralization purification step 2, for example, caustic soda is added as a neutralizing agent to the above-mentioned leachate, and the neutralization treatment is performed at about pH 7. After this neutralization treatment, 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 the neutralized starch is recovered, it is repeated in the melting step 5 in the same manner as in the case of the residue in the starch treatment step 4 described above.

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

First, in the sulfurization step 31, an acid and a sulfurizing agent are added to the above neutralization filtrate to precipitate rhenium contained in the neutralization filtrate as rhenium sulfide. When adding an acid, the amount added is adjusted so that the pH of the reaction solution becomes about 0. Sulfuric acid or hydrochloric acid can be used as the acid to be added, but it is desirable to use sulfuric acid from the viewpoint of freedom of selection of materials used for equipment such as reaction tanks and volatility.

On the other hand, as the sulfide agent, alkali hydrosulfide such as sodium hydrosulfide, alkali sulfide such as sodium sulfide, alkaline earth sulfide such as calcium sulfide, hydrogen sulfide and the like 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 produced by this reaction is preferably a slurry containing precipitated rhenium sulfide by removing the supernatant by standing (decantation) (hereinafter, referred to as a lower rhenium sulfide slurry or simply a slurry). Is obtained.

In the next slurry cleaning step 32, a cleaning liquid having a volume of 5 times or more is added and mixed with the slurry for cleaning. At that time, the acid concentration is 2.0 or less and the pH is 7.0 or less, and the oxidation-reduction potential (measured value when the silver-silver chloride electrode is used as a reference electrode, and the same applies to the subsequent oxidation-reduction potentials. The renium sulfide is washed under the condition of −0.5 V or more and 0.2 V or less. When this acid concentration exceeds 2.0 specifications, rhenium sulfide is redissolved. Further, even if water is added as a cleaning liquid to the acidic rhenium sulfide slurry and the cleaning is repeated, the pH does not exceed 7, so the pH is set to 7 as the upper limit. When the redox potential exceeds 0.2 V, renium sulfide becomes perrhenic acid ion and redissolves. The redox potential can be lowered by adding a strong reducing agent, but since it is not economical, a lower limit of the redox potential of −0.5 V is sufficient. The upper limit of the acid concentration may be limited to the pH value at the time of the 2.0 regulation instead of the 2.0 regulation. This pH value can generally be derived from pH = -log [acid concentration], and in the above case it is 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 liquid is less than 5 times the amount of the slurry on a volume basis, the concentration of sodium sulfate contained in the cleaning liquid during cleaning becomes too high, and the risk of insufficient cleaning increases, and sodium sulfate is used. The amount of carryover to the filter in the subsequent process may increase with the adhering liquid of renium sulfide. There is no particular restriction on the upper limit of the amount of cleaning liquid, but if it exceeds about 15 times, the effect will not increase any more, which is uneconomical. In addition, in order to prevent insufficient cleaning, it is preferable to stir for 30 minutes or more.

The acid concentration during the above cleaning can be adjusted within the above range by using sulfuric acid or hydrochloric acid, but sulfuric acid should be used from the viewpoint of freedom of selection of materials used for equipment such as reaction tanks and volatility. It is desirable to use it. On the other hand, the oxidation-reduction potential can be adjusted by using a sulfide of an alkali metal or an alkaline earth metal, a reducing agent such as hydrogen sulfide or hydrogen. Among these, sodium hydrosulfide or hydrogen sulfide is desirable because it is easily available and can suppress the decomposition of rhenium sulfide into rhenium ions and sulfur ions, and sodium hydrosulfide is more preferable in terms of ease of handling. ..

After cleaning the above slurry, the slurry containing the above cleaning solution is allowed to stand for 2 hours or more for solid-liquid separation. If the standing time is shorter than 2 hours, the solid-liquid separation becomes insufficient, and the possibility that rhenium sulfide contained in the slurry is discharged to the supernatant liquid side increases the possibility of loss. In order to reduce this loss, it is conceivable to reduce the withdrawal amount of the supernatant liquid, which will be described later. In this case, the concentration of the slurry remaining after the withdrawal of the supernatant liquid becomes low, and the filtration time in the solid-liquid separation step 33 of the subsequent step. Therefore, the production efficiency decreases.

Even in the standing state of the slurry cleaning step 32, the acid concentration of the slurry is 2.0 specified or less, the pH is 7.0 or less, and the oxidation-reduction potential is −0.5 V or more and 0, as in the case of the above-mentioned cleaning. It is preferable that the voltage is .2 V or less. It is preferable that the redox potential of the slurry does not exceed 0.2 V during the above-mentioned washing or standing. As a specific adjustment method of the redox potential, measure the redox potential in the washing tank or the standing tank during washing or standing, and when the redox potential is about to exceed 0.2V, Add a reducing agent. Alternatively, a large amount of reducing agent is added to the washing water in advance so that the redox potential does not exceed 0.2 V. In addition, the inside of the tank is purged with nitrogen so that oxygen in the air does not mix with 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 the supernatant liquid. The concentrated slurry having a high concentration of rhenium sulfide remaining by extracting the supernatant liquid is then passed through a filter such as a filter press in the solid-liquid separation step 33 for filtration. After filtering the concentrated slurry, it is preferable to pass a cleaning solution having the same volume or more as the amount of the concentrated slurry passed through the filter through the filter. As a result, the filtered cake is washed, so that the concentration of impurities such as sodium sulfate contained in rhenium sulfide can be further reduced. After washing, the filtered cake is collected 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 filtered cake obtained in the solid-liquid separation step 33 may be returned to the slurry cleaning step 32 again, and the above-mentioned washing and the subsequent solid-liquid separation may be repeated. In this case, by maintaining the acid concentration and the redox potential of the slurry during washing and standing still within the above ranges, the loss due to the redissolution of rhenium can be suppressed. By the method for recovering rhenium sulfide described above, high-purity rhenium sulfide can be efficiently recovered from a substance containing rhenium such as sulfide of rhenium accompanying exhaust gas discharged from a smelting furnace of a non-ferrous metal smelting plant. ..

[Example 1]
Sulfide treatment with sodium hydrosulfide was performed on the cleaning wastewater from the scrubber that washes the exhaust gas containing sulfurous acid gas generated in the copper smelting plant with water, and the sulfide starch containing renium was recovered. The sulfide starch was treated according to 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 for repulping, and steam was blown together with air so that the temperature of the obtained slurry became 70 ° C., and oxidative leaching was performed. As a result, a leachate having a pH of about 0 was obtained (leaching step 1). This leachate was neutralized by adding 20% by mass of caustic soda so that the pH became 6.8 at 25 ° C. to produce a neutralized starch. This neutralized starch was removed using a nutche covered with filter paper to obtain a neutralized filtrate (neutralization purification step 2).

The above neutralized filtrate was subjected to a rhenium recovery step according to the step flow shown in FIG. Specifically, first, 70% sulfuric acid was added so that the acid concentration became 1.0 specified. At this time, the pH of the reaction solution was about 0. Next, sodium hydrosulfide, which is 1.05 times the stoichiometric amount required to produce rhenium sulfide from the rhenium contained in the neutralized filtrate, is added to perform sulfurization treatment to produce rhenium sulfide, which is left as it is for 2 hours. It was allowed to stand (sulfurization step 31).

After the lapse of the above 2 hours, an amount corresponding to 85% by volume of the whole was withdrawn from the upper part as a supernatant liquid. To the slurry containing the remaining renium sulfide, 10 times the volume of washing water was added, and the mixture was stirred for 40 minutes (slurry washing step 32). As the washing water, 70% sulfuric acid and sodium hydroxide were used to adjust the acid concentration to 1.0 and the oxidation-reduction potential to 0.14 V using the silver-silver chloride electrode as a reference electrode. After stirring, the mixture was allowed to stand for 3 hours. During standing, the inside of the container was purged with nitrogen to prevent oxidation by air.

During the above stirring and standing, the redox potential of the slurry is measured, and when the redox potential (silver-silver chloride reference electrode) exceeds 0.15 V, a sodium hydroxide solution is added. I prepared it, but it did not exceed 0.15V. That is, the acid concentration of the slurry during the stirring and standing still was 1.0 regulation (pH is 0), and the redox potential was 0.14V.

After standing for the above 3 hours, an amount corresponding to 85% of the whole was withdrawn as a supernatant from the upper part, and a 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 filtered cake obtained by filtering the concentrated slurry, wash water having the acid concentration and oxidation-reduction potential adjusted is passed through the filter in the same volume as the concentrated slurry. did. The rhenium sulfide product of Example 1 was prepared by drying this filtered cake with a dryer.

[Example 2]
The slurry containing renium sulfide was washed with washing water that was weakly basic and had a high redox potential to prepare the renium sulfide product of Example 2. Specifically, the acid concentration at the time of adding sulfuric acid to the neutralized filtrate should be 2.5 specified instead of 1.0, and the amount of sodium hydrosulfide added should be 1. The amount should be 1.1 times instead of 05 times, the amount of supernatant extracted to obtain the slurry containing rhenium sulfide and the concentrated slurry should be 80% instead of 85%, and the pH of the washing water should be 7.5. The rhenium sulfide product of Sample 2 was prepared in the same manner as in Sample 1 above, except that ion-exchanged water having an oxidation-reduction potential of 0.4 V was added to the slurry 5 times by volume. The acid concentration of the slurry during stirring and standing was 0.5 (pH was 0.3), and the redox potential was 0.11 V.

[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. As the slurry cleaning conditions, the conditions of Example 2 were applied. The acid concentration during stirring and standing was approximately pH 3. When the redox potential exceeded −0.07V, sodium hydrosulfide was added to bring the redox potential to −0.07V or less. The redox potential during standing was less than -0.07V. After standing, the slurry is filtered with a filter, and the same volume of cleaning liquid as the slurry whose acid concentration is pH 3 with dilute sulfuric acid and the oxidation-reduction potential is adjusted to -0.07V with sodium hydroxide is passed through the filter. , The renium 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. As the slurry cleaning conditions, the conditions of Example 2 were applied. The acid concentration during stirring and standing was approximately pH 6. When the redox potential exceeded −0.3 V, sodium hydrosulfide was added to bring the redox potential to −0.3 V or less. The redox potential during standing was less than -0.3 V. After standing, the slurry is filtered with a filter, and the same volume of cleaning liquid as the slurry whose acid concentration is pH 6 with dilute sulfuric acid and the oxidation-reduction potential is adjusted to -0.3 V with sodium hydroxide is passed through the filter. , The renium 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. As the slurry cleaning conditions, the conditions of Example 2 were applied. The acid concentration during stirring and standing was approximately pH 3. When the redox potential exceeded −0.3 V, sodium hydrosulfide was added to bring the redox potential to −0.3 V or less. The redox potential during standing was less than -0.3 V. After standing, the slurry is filtered with a filter, and the same volume of cleaning liquid as the slurry whose acid concentration is pH 3 with dilute sulfuric acid and the oxidation-reduction potential is adjusted to −0.3 V with sodium hydroxide is passed through the filter. , The renium sulfide product of Example 5 was obtained.

[Comparative Example 1]
Up to the sulfurization step 31, a slurry containing renium sulfide was produced in the same manner as in Example 1, and after allowing this to stand for 2 hours, an amount corresponding to 85% by volume of the whole was withdrawn as a supernatant liquid from the upper part, and the remaining renium sulfide was extracted. To the slurry containing the above, a cleaning solution having an acid concentration of 1 specified with 10 times the volume of dilute sulfuric acid was added, and the mixture was stirred for 40 minutes. The acid concentration during stirring was 1.0. The redox potential was not adjusted during stirring and standing. Therefore, the redox potential was initially 0.16 V, but gradually oxidized and the redox potential became 0.4 V at the end of stirring. After stirring, the mixture was allowed to stand for 3 hours. Nitrogen was not purged in the container during stirring and standing.

After standing for 3 hours, an amount corresponding to 85% of the whole was withdrawn from the upper part as a supernatant, and the remaining concentrated slurry in which rhenium sulfide was more concentrated was passed through a filter and filtered. In order to wash the obtained filtered cake, a washing solution prepared with dilute sulfuric acid having an acid concentration of 1.0 was passed through the filter in the same volume as the above-mentioned concentrated slurry. The redox potential of the cleaning solution was 0.4V. The rhenium sulfide product of Comparative Example 1 was prepared by drying this filtered cake with a dryer.

[Comparative Example 2]
Up to the sulfurization step 31, a slurry containing rhenium sulfide was produced in the same manner as in Example 2, and then in the slurry cleaning step 32, the same amount of ion-exchanged water as in Example 2 was added in the same amount as in Example 2 and replaced with 40 minutes. Stirred for 1 hour. After that, 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 redox potential was initially 0.01 V, but gradually participated and the redox potential became 0.4 V at the end of stirring. After stirring, the mixture was allowed to stand for 3 hours. Nitrogen was not purged in the container during stirring and standing.

After standing, the slurry was filtered with a filter, and a washing solution having the same volume as the slurry adjusted to an acid concentration of pH 3 with dilute sulfuric acid was passed through the filter to obtain a rhenium sulfide product of Comparative Example 2. The redox potential of the cleaning solution was 0.4V. The rhenium sulfide product of Comparative Example 2 was prepared by drying this filtered cake with a dryer.

[Comparative Example 3]
Up to the sulphurization step 31, a slurry containing rhenium sulfide is produced in the same manner as in Example 1 above, and then the slurry is directly passed through a filter in the solid-liquid separation step 33 without being treated in the slurry cleaning step 32 to sulphurize. A filtered cake of rhenium was obtained. The rhenium sulfide product of Comparative Example 3 was prepared by drying this filtered cake with a dryer.

During the production of rhenium sulfide of Examples 1 to 5 and Comparative Examples 1 to 3, the content of rhenium contained in the supernatant liquid (excluding the case of Comparative Example 3), the filtrate and the rhenium sulfide product after washing was analyzed by ICP. The rhenium grade and the rhenium recovery rate were obtained by measuring with the device. At that time, all the rhenium sulfide in the rhenium sulfide product was converted as _{direnium heptasulfide (VII) (Re 2} S _7). The rhenium sulfide ratio and the sodium sulfide ratio were determined from the mass of the rhenium sulfide product, the mass of direnium heptasulfide in the rhenium sulfide product, and the mass of sodium sulfide. The rhenium grades, rhenium sulfide ratios and recovery rates of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 below.

From the results in 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 grade could be recovered with a high recovery rate. On the other hand, in Comparative Examples 1 and 2 in which the rhenium sulfide was washed but the redox potential was not adjusted, the rhenium grade of the rhenium sulfide product was high, but the recovery rate was poor. Further, in Comparative Example 3, since the rhenium sulfide was not washed, the rhenium recovery rate was high, but the rhenium grade in the rhenium sulfide product was low.

1 Leaching process 2 Neutralization purification process 3 Rhenium recovery process 31 Sulfurization process 32 Slurry cleaning process 33 Solid-liquid separation process

Claims (4)

A leaching step of oxidatively leaching an object to be treated containing renium, arsenic and cadmium to obtain a leachate, and neutralizing the leachate with an alkali to produce a neutralized precipitate containing arsenic and cadmium. Rhenium sulfide including a neutralization purification step of removing the neutralized precipitate from the sum filtrate and a rhenium recovery step of sulphurizing the neutralized filtrate to recover the renium contained in the neutralized filtrate as renium sulfide. It ’s a collection method,
In the renium recovery step, a cleaning solution is added to the slurry before recovering the rhenium sulfide to obtain an acid concentration of 2.0 or less and a pH of 7.0 or less, and an oxidation-reduction potential (silver-silver chloride reference electrode). A method for recovering rhenium sulfide, which comprises 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, the washing liquid is added to the slurry containing rhenium sulfide after removing the obtained supernatant liquid, and the mixture is stirred under the conditions of the acid concentration and the oxidation-reduction potential. The method for recovering rhenium sulfide according to claim 1, wherein the rhenium is washed by allowing it to stand. The slurry containing rhenium sulfide after being washed with the washing liquid is passed through a filter to be filtered, and then the washing liquid having the acid concentration and the oxidation-reduction potential is passed through the filter cake in the filter for washing. The method for recovering rhenium sulfide according to claim 2, wherein the method is characterized by the above. The claim is characterized in that the raw material containing renium, arsenic and cadmium is recovered from the washing waste liquid discharged from the washing step of washing the exhaust gas containing sulfur dioxide gas generated from the non-ferrous metal smelting factory with water. The method for producing renium sulfide according to any one of 1 to 3.

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