JP2015113267A - Separation/recovery method of tellurium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation/recovery method of tellurium, with which separation of impurity metals is easy and a recovery rate of tellurium is high.SOLUTION: Provided is a separation/recovery method of tellurium comprising: a step of mixing a tellurium raw material into hydrochloric acid, and oxidize tellurium in the presence of an oxidizing agent and make it leach; a step of precipitating tellurium by neutralizing the leachate containing tellurium to pH 1.5 to 7.0; a purification step where a sulfidizing agent is added to a solution, obtained by dissolving the above precipitate with alkali, to precipitate and separate impurity metals in the solution; a step of removing selenium where the solution after the purification step is made strongly acidic and a reducing agent is added to precipitate and separate selenium in the solution at an oxidation-reduction potential of 350 mV or more; and a step of reduction/precipitation of tellurium in the solution by adding a reducing agent to the solution from which selenium has been removed and making the oxidation/reduction potential less than 350 mV.

Description

The present invention relates to a method for efficiently separating and recovering tellurium from tellurium-containing materials such as copper telluride and tellurium reducing soot.

As a by-product of electrolytic refining of copper, copper telluride is produced in many copper smelters around the world and used as a raw material for refined tellurium. Recently, in addition to copper telluride, as a by-product of the wet precious metal recovery process, reduced soot containing tellurium and selenium as by-products has been produced as a by-product and has begun to be used as a raw material for refined tellurium.

A dry method or a wet method is known as a method for recovering tellurium from copper telluride (Non-patent Document 1). In any of these methods, copper telluride is oxidized in an alkaline region to convert tellurium into water-soluble sodium tellurite and separated from hardly soluble copper hydroxide. However, since copper telluride generally contains a small amount of selenium, and selenium also exists as a water-soluble selenite ion, it is difficult to separate selenium and tellurium in this state. In order to separate selenium and tellurium, the alkaline leachate is neutralized with mineral acid (pH 6) to precipitate crude tellurium oxide (TeO ₂ ) to separate it from selenium in the liquid, and this crude tellurium oxide precipitate is washed. Dissolution, recrystallization, and the like are performed to obtain purified tellurium oxide, and after the purified tellurium oxide is dissolved, metal reduction can be obtained by chemical reduction or electrochemically.

Patent Document 1 (Japanese Patent Laid-Open No. 2011-214092) describes a treatment method such as tellurium reducing soot. In this method, reduced soot containing selenium, tellurium and the like is made into a sodium hydroxide aqueous solution slurry, and air is blown into this slurry to create an oxidizing atmosphere to elute selenium and tellurium by alkaline oxidation. Mineral acid is added to the eluate to neutralize it, tellurium is allowed to settle, and selenium in the liquid is separated and recovered.

In Patent Document 2 (Patent No. 3616314: JP-A-2001-316735), tellurium-containing materials are combined with copper telluride as necessary, and alkali leached and then neutralized to precipitate tellurium dioxide. And a method of recovering tellurium from the leaching solution by electrolytic collection is described.

In Patent Document 3 (Japanese Patent No. 4574825: JP 2002-105553 A), sulfur is added to copper telluride, and heat treatment (500-600 ° C.) is performed to convert copper to copper sulfide (CuS, Cu ₉ S _5). And then heating to 200 ° C. to 1000 ° C. under reduced pressure to volatilize tellurium.

However, in the treatment method of Patent Document 1, 2-5 times equivalent of caustic soda is used for selenium and tellurium, and the oxidative leaching is as long as 1-2 days. In addition, since selenium is eluted together with tellurium in the leaching process, tellurium is precipitated as TeO ₂ in order to separate these, and this precipitation can be separated to a certain extent by repeating washing several times, but it is sufficiently separated from tellurium. Selenium cannot be separated.

Further, in the treatment method of Patent Document 2, when copper telluride is oxidized and leached with caustic soda solution, the copper content that occupies about half of the raw material becomes copper hydroxide and covers the surface of copper telluride, so that dissolution of tellurium is hindered. And leaching takes longer and some tellurium remains undissolved. Also, some of the tellurium that is leached is oxidized to hexavalent and may precipitate during leaching in the form of sodium tellurate (Na ₂ TeO ₄ ), which is sparingly soluble in caustic soda solution. Furthermore, part of the coexisting selenium may be oxidized to hexavalent, and it takes a long time to reduce selenium by SO ₂ reduction.

JP 2011-214092 A Japanese Patent No. 3616314 Japanese Patent No. 4557425

Recent Trends in Extraction of Selenium & Tellurium from Electrolytic Copper Slimes, NML Technical Journal, Vol.12, November 1970, pp.101-110

The present invention solves the above-mentioned problems in the conventional processing method, is easy to separate impurity metals, has a high recovery rate of tellurium, and coexists when, for example, copper telluride is used as a raw material. Provided is a tellurium separation and recovery method which has a high copper leaching rate and can reduce the occurrence of copper soot to about 1/10 of the conventional one.

The treatment method of the present invention is a tellurium separation and recovery method having the following constitution.
[1] A step of mixing tellurium-containing raw material with hydrochloric acid to oxidize and leach tellurium in the presence of an oxidizing agent, a step of neutralizing the pH of the leachate containing tellurium to 1.5 to 7.0 to precipitate tellurium, A solution obtained by adding a sulfiding agent to a solution obtained by dissolving the precipitate in an alkali solution to precipitate and separate impurity metals in the solution, making the solution after the solution step strongly acidic, adding a reducing agent and adding a redox potential ( Ag / AgCl electrode) Deselenium process that precipitates and separates selenium in the liquid at 350 mV or higher, tellurium in liquid to reduce the redox potential (Ag / AgCl electrode) to less than 350 mV by adding a reducing agent to the selenium-removed solution A method for separating and recovering tellurium, characterized by comprising a step of reducing and precipitating.
[2] In the oxidation leaching step, tellurium is oxidized and leached by mixing a tellurium-containing raw material with hydrochloric acid to obtain a leaching slurry having an initial concentration of solids of 500 g / L or less and an initial concentration of hydrochloric acid of 4 to 6 mol / L. The method for separating and recovering tellurium according to 1].
[3] In the oxidative leaching step, tellurium as described in [1] or [2] above, wherein an oxidant is added to the leached slurry and the redox potential (Ag / AgCl electrode) is set to 400 to 1100 mV to leached tellurium. Separation and recovery method.
[4] The tellurium separation and recovery method according to any one of [1] to [3] above, wherein hydrochloric acid is added to the solution after the liquid purification step to adjust the pH to −1 to 2 in the deselenization step.
[5] In the de-selenium step, 10 to 300 g / L of a reducing agent is added to the strongly acidic solution after the liquid purification step to adjust the oxidation-reduction potential (Ag / AgCl electrode) of the solution to 350 mV to 360 mV. ] To tellurium separation and recovery method according to any one of [4] above.
[6] In the reduction deposition step of tellurium, the reducing agent is added to the solution after the deselenization step until the oxidation-reduction potential (Ag / AgCl electrode) becomes 300 mV to less than 350 mV to reduce and deposit tellurium in the solution [ [1] A method for separating and recovering tellurium according to any one of [5] above.
[7] The tellurium separation and recovery method according to any one of [1] to [6] above, wherein the tellurium-containing raw material is copper telluride or tellurium reduced soot.

In the treatment method of the present invention, tellurium contained in the raw material is oxidized and leached with hydrochloric acid, so that the leaching time can be greatly shortened. For example, the conventional alkali leaching requires a leaching time of 16 to 24 hours, but the hydrochloric acid leaching time of the present invention may be about 30 to 40 minutes.

The treatment method of the present invention can increase the leaching rate of copper contained in the raw material to almost 100%. Also, when tellurium is precipitated by adjusting the pH of the solution to 1.5 to 7.0 after leaching, copper does not settle in this pH range and remains in the filtrate, so almost all of the leached copper is recovered from the filtrate. can do. The recovered copper can be processed in the copper smelting process.

In conventional alkali leaching, copper in the raw material forms copper hydroxide and is contained in the residue, which is filtered and separated from the tellurium of the filtrate, but this alkaline slurry is difficult to filter, and more than 10% of the tellurium Since it is taken up by the copper residue, the tellurium recovery rate is significantly reduced. On the other hand, the treatment method of the present invention is a method in which tellurium oxychloride is precipitated and separated. This tellurium oxychloride is easy to filter and easy to treat, and has good separability against impurity metals.

In the treatment method of the present invention, in oxidation leaching using hydrochloric acid, the oxidation-reduction potential (ORP) can be easily controlled, and the leaching selectivity to copper telluride is good, for example, the dissolution of selenide can be suppressed. Moreover, even if a small amount of selenium or silver is eluted in the oxidative leaching, by adjusting the pH of the slurry to 1.5 to 7.0 after leaching, tellurium selectively settles in this pH range, And since silver remains in solution, tellurium can be easily separated from these impurities.

The schematic process drawing of the processing method of the present invention. The graph which shows the relationship between pH and tellurium ion concentration. The graph which shows the relationship between pH and the dissolution amount of arsenic, selenium, silver, and copper. 3 is an XRD diffraction chart of the neutralized starch of Example 2. FIG.

Hereinafter, the present invention will be specifically described based on embodiments. The processing steps of the tellurium separation and recovery method of the present invention are shown in FIG. In the following description,% is mass%. The redox potential is based on the Ag / AgCl electrode.

The treatment method of the present invention comprises a step of mixing tellurium-containing raw material with hydrochloric acid and oxidizing and leaching tellurium in the presence of an oxidizing agent, and neutralizing the pH of the leachate containing tellurium to 1.5 to 7.0 to obtain tellurium. Precipitation step, a purification step of adding a sulfiding agent to a solution in which the precipitate is dissolved in an alkali to precipitate and separate impurity metals in the solution, making the solution after the purification step strong acid, adding a reducing agent A de-selenium step of precipitating and separating selenium in the liquid at a redox potential of 350 mV or more, and a step of reducing and precipitating tellurium in the liquid to a redox potential of less than 350 mV by adding a reducing agent to the solution from which selenium has been removed. This is a method for separating and recovering tellurium.

As the tellurium-containing raw material, for example, copper telluride or tellurium reducing soot is used. Copper telluride is obtained as a byproduct of the electrolytic refining of copper and contains about 50% tellurium and copper each. Further, tellurium reduced soot is obtained as a by-product of the wet noble metal recovery step, and contains several percent of selenium, copper, arsenic and silver in addition to the main component tellurium.

[Tellurium leaching process]
A tellurium-containing raw material is mixed with hydrochloric acid to form a slurry, and an oxidizing agent is added to the slurry to oxidize and leach tellurium. When copper telluride or the like is used as the tellurium-containing raw material, almost all of tellurium and copper in the raw material are leached by this hydrochloric acid leaching.

The initial solid content concentration (solid content concentration in the leaching process) of the slurry is preferably 500 g / L or less. When the initial solid content concentration is higher than 500 g / L, there is too much solid content, and oxidation leaching does not proceed stably. The initial solid content concentration is more preferably 100 g / L to 300 g / L.

The initial hydrochloric acid concentration (hydrochloric acid concentration in the leaching step) of the slurry is preferably 4 mol / L to 6 mol / L. If the initial hydrochloric acid concentration is lower than 4 mol / L, tellurium leaching may be insufficient when the slurry concentration is close to 300 g / L. On the other hand, when the initial hydrochloric acid concentration exceeds 6 mol / L, the concentration of free hydrochloric acid after leaching increases, and the consumption of the neutralizing agent necessary for neutralization increases.

As an oxidizing agent, hydrogen peroxide (H ₂ O ₂ ), sodium chlorate (NaClO ₃ ), or the like can be used. The addition amount of the oxidizing agent is preferably in a range where the oxidation-reduction potential (ORP) is 400 to 1100 mV (Ag / AgCl electrode). If the ORP is less than 400 mV, the tellurium is not sufficiently oxidized and leached.

The temperature of the leaching slurry is preferably 60 ° C to 90 ° C. When the solid content concentration and hydrochloric acid concentration of the slurry are in the above ranges, the above temperature range can be maintained by the heat of oxidation reaction. Note that the reactor may be provided with a heating means and a cooling mechanism so as to cope with changes in the leaching conditions.

In the above oxidative leaching conditions, the leaching time is about 30 minutes to 2 hours. The leaching time varies depending on the rate of addition of the oxidant and the heat radiation or cooling ability of the reactor, so it is preferable to determine the immersing time in consideration of these.

[Tellurium precipitation (neutralization) process]
An alkali such as caustic soda is added to the leachate containing tellurium to neutralize the pH of the leachate to 1.5 to 7.0, thereby precipitating tellurium in the liquor. In the Te-HCl-NaOH system, the change in tellurium solubility when the pH is changed is shown in FIG. As shown in the figure, tellurium precipitates because the solubility of tellurium is low in the range of about pH 1.5 to about 7.0. When the pH is less than 1.5 or more than pH 7.0, tellurium has a high solubility, resulting in insufficient precipitation.

By this neutralization treatment, tellurium in the liquid is precipitated by forming tellurium oxychloride (Te ₆ O ₁₁ Cl ₂ ), for example, as shown in the following formula [1].
6H ₂ TeCl ₆ + 34NaOH → Te ₆ O ₁₁ Cl ₂ ↓ + 34NaCl + 23H ₂ O …… [1]

The slurry leached with copper telluride or tellurium reducing soot contains copper, arsenic, selenium, silver and the like together with tellurium. FIG. 3 shows changes in these metal ion concentrations due to changes in the pH of the leachate. As shown in the figure, selenium and arsenic are likely to precipitate when the pH is 2.5 or higher. Therefore, in order to enhance the effect of separating selenium and arsenic from tellurium, neutralization to pH 1.5 to 2.5 is preferable.
On the other hand, since copper and silver in the liquid remain in the liquid even at a pH of 2.5 or higher, neutralizing the pH of the leaching slurry to 1.5 to 7.0 selectively precipitates tellurium and Can be separated from copper and silver.

A treatment temperature higher than room temperature is desirable because the filterability of the tellurium oxychloride precipitate is increased. It is good to leave it for several hours to overnight after pH adjustment. Moreover, it is preferable to start the neutralization treatment while the slurry temperature immediately after the hydrochloric acid oxidation leaching is higher than the room temperature, because the labor required for reheating can be saved.

Since most of the copper is contained in the filtrate, it can be recovered by post-treatment of the filtrate. On the other hand, since the amount of copper incorporated into the tellurium oxychloride precipitate is small, the amount of copper soot generated in the post-treatment of tellurium precipitation is reduced to about 1/10 of the conventional treatment method, and the amount of tellurium incorporated into the copper soot is reduced. The amount of loss is also greatly reduced.

[Solid-liquid separation process]
The tellurium oxychloride precipitate is recovered by filtration. Most of copper, selenium, arsenic, silver and the like are contained in the filtrate without being precipitated, so that tellurium and these impurity metals can be separated into solid and liquid. Tellurium oxychloride precipitates have better filterability than alkaline slurries such as copper hydroxide, so that separation between tellurium and the above impurity metals is good. For example, if the tellurium oxychloride precipitate is sufficiently filtered, the transfer rate of tellurium to the filtrate can be suppressed to 1% or less.

To the filtrate from which the tellurium oxychloride has been separated, calcium carbonate or the like is added to precipitate the impurity metal. By this waste water treatment, for example, copper in the liquid is precipitated by forming copper hydroxide as shown in the following formula [2], which is removed by filtration.
CuCl ₂ + CaCO ₃ + H ₂ O → Cu (OH) ₂ ↓ + CaCl ₂ + CO ₂ …… [2]

[Tellurium recovery process]
Metal tellurium can be recovered from the recovered tellurium oxychloride precipitate, for example, by the following processing steps.
Dissolve the tellurium oxychloride precipitate in an alkali to separate the residue ( alkali dissolution treatment ), add a sulfiding agent to the alkaline solution to precipitate and separate the impurity metal in the solution ( sulfurized and purified liquid treatment ). Add the reducing agent by making the alkaline solution treated with liquid strong acid, add selenium in the solution at a redox potential of 350 mV or more to separate it ( deselenium reduction treatment ), add the reducing agent to the solution from which selenium has been removed, Metal tellurium is recovered by reducing and precipitating tellurium in the liquid at an oxidation-reduction potential of less than 350 mV ( tellurium reduction treatment ).

Alkaline dissolution treatment Tellurium oxychloride precipitate is dissolved in caustic soda. Copper, silver, etc. contained in a small amount in the precipitate remain as solids without dissolving. The liquid temperature may be about room temperature to about 60 ° C., and the pH of the solution is preferably about 10 to 13. When the pH is less than 10, the dissolution of tellurium oxychloride is insufficient. When the pH is higher than 13, the elution of heavy metals such as copper contained in the precipitate proceeds, which is not preferable.

Sulfurized liquid treatment A sulfurizing agent such as sodium hydrosulfide (NaHS) is added to the alkaline solution to precipitate and separate impurity metals in the liquid. Impurity metals such as copper, lead, iron, and silver in the liquid form a sulfide under the pH of 10 to 13 and precipitate, and can be filtered to separate these impurity metals.

Deselenium reduction treatment An acid is added to the alkali solution that has been subjected to the purification treatment to make it strongly acidic. For example, hydrochloric acid is added to the alkaline solution to make the solution pH strongly acidic from −1 to 2.

A reducing agent (NaHSO ₃ or the like) is added to the strongly acidic liquid to reduce and precipitate selenium in the liquid at an oxidation-reduction potential of 350 mV or higher, preferably 350 mV to 360 mV. The selenium precipitate is collected by filtration. Tellurium remains in the liquid.
The concentration of the reducing agent is preferably 10 to 300 g / L (0.05 to 1.5 gram equivalent / L with respect to selenium). If the concentration of the reducing agent is lower than 10 g / L, the amount added is not preferable. On the other hand, when the concentration of the reducing agent is higher than 300 g / L, the oxidation-reduction potential around the added reducing agent is locally reduced to less than 350 mV, and tellurium is reduced and precipitated together with selenium, and is taken into the selenium precipitate. This is not preferable because the loss of tellurium increases.

Tellurium reduction treatment <br/> solution to the reducing agent to remove selenium (NaHSO _3, etc.) is added, than the redox potential 350 mV, is preferably reduced tellurium in the liquid be less than 300mV~350mV precipitation. The tellurium precipitate is collected by filtration. The recovered tellurium precipitate can be washed with warm water, dehydrated and dried to obtain metal tellurium with 3N purity. If the redox potential is higher than 350 mV, tellurium does not precipitate.

Examples of the present invention will be described below. The concentrations of tellurium, selenium and copper were measured using ICP-AES. The redox potential is based on the Ag / AgCl electrode.

[Example 1]
A tellurium-containing solid (Te 40%) dry weight of 700 g was mixed with 2 L of a hydrochloric acid aqueous solution (HCl 6 mol) to form a slurry and heated to 40 ° C. Next, while monitoring the slurry temperature and oxidation-reduction potential, about 1 L of hydrogen peroxide solution (35% concentration of H ₂ O ₂ ) (1.2 times equivalent to the amount required for oxidation of Cu and Te) was added. The oxidation-reduction potential of the slurry increased to 600 to 1000 mV (vs. Ag / AgCl electrode), and the slurry temperature began to decrease after reaching a maximum of 80 ° C. Next, while this slurry was stirred, caustic soda solution (NaOH 48% concentration) was added until the pH reached 0.5 to 9.0, and stirring was continued for about 1 hour to produce tellurium precipitation. This precipitate was collected by solid-liquid separation. The tellurium recovery rate was determined based on the recovered precipitation. The results are shown in Table 1.

As shown in Table 1, the tellurium recovery rate is 95% or more in the pH range of the slurry from 1.5 to 7.0. On the other hand, when the slurry has a pH of less than 1.5 or a pH of 8.0 or more, the tellurium recovery rate decreases rapidly.

[Example 2]
Copper telluride (Te44%, Cu40%, Se0.3%) dry weight of 660 g was mixed with 2 L hydrochloric acid aqueous solution (HCl 6 mol) to make a slurry and heated to 40 ° C. Next, while monitoring the slurry temperature and oxidation-reduction potential, about 1 L of hydrogen peroxide solution (35% concentration of H ₂ O ₂ ) (1.2 times equivalent to the amount required for oxidation of Cu and Te) was added. The oxidation-reduction potential of the slurry increased to 640 mV (vs. Ag / AgCl electrode), and the slurry temperature began to decrease after reaching a maximum of 80 ° C. Next, while stirring this slurry, about 90 ml of caustic soda solution (NaOH 48% concentration) was added until pH 2.0, and stirring was continued for about 1 hour to form a precipitate. The slurry temperature at the end of stirring was about 50 ° C. The slurry temperature after standing for 4 hours was lowered to 30 ° C., and solid-liquid separation was performed using a suction filter.
A precipitate having a dry weight of 450 g was recovered, and a 2.9 L filtrate was recovered.
Tellurium concentration and copper concentration in the filtrate, tellurium concentration and copper concentration in the precipitate were measured. The results are shown in Table 2.

As shown in Table 2, 90% or more of the copper in the raw material remains in the filtrate, while 98.5% of tellurium is contained in the precipitate and is neutralized so that the slurry has a pH of 2.0. As a result, the result of high separation between tellurium and copper was obtained.

An XRD diffraction chart of the neutralized starch recovered in Example 2 is shown in FIG. As shown, this precipitate has a peak consistent with tellurium oxychloride (Te ₆ O ₁₁ Cl ₂ ), indicating that tellurium forms tellurium oxychloride. Further, copper in the starch has a peak corresponding to copper chloride (CuCl ₂ ), but its strength is low, and most of the copper is contained in the filtrate as shown in Table 2.

Example 3
750 g (water content 40%) of the neutralized starch (tellurium oxychloride) of Example 2 was dissolved in a caustic soda solution (20% concentration, 2.4 L). This tellurium solution (2.35 L, Te: 121 g / L, Cu: 50 ppm) and copper residue (7.5 g dry, Cu content 60%, Te content 6%) were separated by filtration. From this result, 97.5% or more of tellurium eluted with respect to 100% of tellurium in copper telluride and transferred to an alkali solution.

Example 4
A precipitate formed by adding sodium hydrosulfide (NaHS) to the alkali solution (2.35 L) of Example 3 was separated by filtration. Hydrochloric acid was added to the filtrate (2.3 L) to make it strongly acidic (pH = 0). Further, using sodium hydrogen sulfite (NaHSO ₃ ) solution having a concentration of 10 g / L to 300 g / L, the amounts shown in Table 3 were added. Then, selenium was reduced and precipitated at an oxidation-reduction potential of 360 mV. This was separated by filtration, and the recovered amount of selenium and the tellurium content were examined. The results are shown in Table 3.

As shown in Table 3, in sample Nos. 2 to 4 using sodium hydrogen sulfite having a concentration of 10 g / L to 300 g / L, the amount of tellurium incorporated into the precipitated selenium precipitate is 1.7 g to 12 g. In sample Nos. 5 to 6 using sodium hydrogen sulfite of 340 g / L and 400 g / L, the amount of tellurium incorporated into the selenium precipitate is 27 to 50 g, which is remarkably increased.

Example 5
A precipitate formed by adding sodium hydrosulfide (NaHS) to the alkali solution (2.35 L) of Example 3 was separated by filtration. Hydrochloric acid was added to the filtrate (2.3 L) to make it strongly acidic, pH was set to 0, and sodium hydrogen sulfite (NaHSO ₃ ) solution having a concentration of 300 g / L was added, and the amount of sodium bisulfite shown in Table 4 was added. Selenium was reduced and precipitated at an oxidation-reduction potential of 340 mV to 365 mV. This was separated by filtration, and the recovered amount of selenium and the tellurium content were examined. The results are shown in Table 4.
As shown in Samples 11 and 12, when the oxidation-reduction potential is lower than 350 mV, the tellurium content in the deposited selenium precipitate increases.

Example 6
For sample No. 3 of Example 4, sodium hydrogen sulfite (NaHSO ₃ ) in a filtrate (strongly acidic) from which selenium was separated by filtration was added, and tellurium was reduced and precipitated at a redox potential of 300 mV to 355 mV. The tellurium precipitate was separated into solid and liquid, washed with warm water, dehydrated and dried to recover metal tellurium. The recovered amount of tellurium is shown in Table 5. Thus, if the redox potential is higher than 350 mV, tellurium cannot be reduced sufficiently.

Example 7
Tellurium reduced soot (Te 93%, Se 3.8%) 200 g dry weight was mixed with 2 L hydrochloric acid aqueous solution (HCl 4 mol) to make a slurry and heated to 40 ° C. Next, while observing the slurry temperature and oxidation-reduction potential, about 240 cc of hydrogen peroxide solution (35% concentration of H ₂ O ₂ ) (1.2 times equivalent to the amount required for Te oxidation) was added. The oxidation-reduction potential of the liquid increased to 700 mV (vs. Ag / AgCl electrode), and the slurry temperature began to decrease after reaching a maximum of 70 ° C. Next, while stirring the slurry, caustic soda was added until the pH reached 2.0, and stirring was continued for about 1 hour to produce a neutralized starch. The slurry after standing for 4 hours was subjected to solid-liquid separation to obtain a neutralized filtrate and neutralized starch (Table 6). As shown in Table 6, it can be seen that about 68% of selenium in the raw material and 98% or more of tellurium are present in the neutralized starch. Next, the neutralized starch was mixed with an aqueous NaOH solution to dissolve tellurium oxychloride. The tellurium concentration of this alkaline solution was 121 g / L (97.5% with respect to tellurium in the raw material), and the selenium concentration was 63 ppm (1.3% with respect to selenium in the raw material).

Example 8
The precipitate formed by adding sodium hydrosulfide (NaHS) to the alkaline solution (1.5 L) of Example 7 was filtered, and hydrochloric acid was added to the filtrate (2 L) to make it strongly acidic (pH = 0). Sodium bisulfite (NaHSO ₃ ) solution was added and selenium was reduced and precipitated at an oxidation-reduction potential of 360 mV, which was separated by filtration to recover 7.6 g of selenium.
On the other hand, hydrochloric acid is added to (2 L) to the filtrate from which selenium has been separated to make it strongly acidic (pH = 0), and further sodium bisulfite (NaHSO ₃ ) solution is added to reduce and tellurium at a redox potential of 300 mV. This was separated by filtration to recover 186 g of 3N tellurium.

Claims (7)

A step of mixing tellurium-containing raw material with hydrochloric acid to oxidize and leach tellurium in the presence of an oxidizing agent; a step of neutralizing the pH of the leachate containing tellurium to 1.5 to 7.0 to precipitate tellurium; The solution in which the solution is alkali-dissolved is added with a sulfidizing agent to precipitate and separate the impurity metals in the solution, and the solution after the solution is made strongly acidic, and the reducing agent is added to the redox potential (Ag / AgCl Electrode) having a de-selenium step of precipitating and separating selenium in the liquid at 350 mV or more, and adding a reducing agent to the solution from which the selenium has been removed to reduce the oxidation-reduction potential to less than 350 mV and reducing and depositing tellurium in the solution. A method for separating and recovering tellurium.
The tellurium-containing raw material is mixed with hydrochloric acid in the oxidative leaching step, and tellurium is oxidatively leached into a leaching slurry having an initial concentration of solids of 500 g / L or less and an initial concentration of hydrochloric acid of 4 to 6 mol / L. How to separate and recover tellurium. The method for separating and recovering tellurium according to claim 1 or 2, wherein, in the oxidative leaching step, tellurium is leached by adding an oxidizing agent to the leaching slurry and setting the redox potential (Ag / AgCl electrode) to 400 to 1100 mV. The method for separating and recovering tellurium according to any one of claims 1 to 3, wherein hydrochloric acid is added to the solution after the liquid purification step to bring the pH to -1 to 2 in the deselenization step. In the de-selenium step, 10 to 300 g / L of a reducing agent is added to the strongly acidic solution after the liquid purification step to adjust the redox potential (Ag / AgCl electrode) of the solution to 350 mV to 360 mV. 4. The tellurium separation and recovery method according to any one of 4 above. In the reduction deposition step of tellurium, a reducing agent is added to the solution after the de-selenium step until the oxidation-reduction potential (Ag / AgCl electrode) becomes 300 mV to less than 350 mV to reduce and deposit tellurium in the solution. Item 6. The tellurium separation and recovery method according to any one of Items 5 to 6. The tellurium-containing raw material is copper telluride or tellurium reducing soot, The tellurium separation and recovery method according to any one of claims 1 to 6.

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