JP5843069B2 - Tellurium separation and recovery method - Google Patents

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, copper telluride generally contains a small amount of selenium, and selenium is also present as a water-soluble selenite ion, which is difficult to separate from tellurium. In order to separate selenium and tellurium, the alkaline leachate is neutralized with mineral acid (pH 6), and the crude tellurium oxide (TeO ₂ ) is precipitated. The crude tellurium oxide precipitate is washed, dissolved, recrystallized, etc. Purified tellurium oxide is obtained, and after the purified tellurium oxide is dissolved, metal tellurium is obtained by chemical reduction or electrochemically.

Further, a processing method such as tellurium reducing soot described in Patent Document 1 (Japanese Patent Laid-Open No. 2011-214092) is known. 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.

Patent Document 2 (Patent No. 3616314: Japanese Patent Laid-Open No. 2001-316735) describes tellurium dioxide by precipitating tellurium dioxide by neutralizing the tellurium-containing material together with copper telluride if necessary and leaching with alkali. 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 heated 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] Tellurium-containing raw materials are mixed with hydrochloric acid, and tellurium is oxidatively leached in the presence of an oxidizing agent, and the pH of the leachate containing tellurium is adjusted to 1.5 to 2.5 to precipitate tellurium oxychloride. A method for separating and recovering tellurium, wherein the tellurium is recovered by separating the precipitate.
[2] Separation and recovery of tellurium as described in [1] above, wherein the initial slurry concentration of the tellurium-containing raw material is adjusted to 100 to 300 g / L and the initial concentration of hydrochloric acid is adjusted to 4 to 6 mol / L in the oxidation leaching step. Method.
[3] The tellurium separation and recovery method according to the above [1] or [2], wherein the oxidation-reduction potential (Ag / AgCl electrode) is controlled to 600 to 700 mV in the oxidation leaching step.
[4] Tellurium oxychloride is solid-liquid separated and separated from the impurity metal in the filtrate, the recovered tellurium oxychloride is alkali-dissolved to separate the residue, and a sulfiding agent is added to the alkali-dissolved solution. The impurity metal is precipitated and separated, and the purified alkali solution is made strongly acidic, a reducing agent is added, and selenium in the liquid is precipitated and separated at an oxidation-reduction potential of 350 mV or more, and the selenium is removed. The tellurium separation and recovery method according to any one of [1] to [3] above, wherein a reducing agent is added and tellurium in the liquid is reduced and precipitated at an oxidation-reduction potential of less than 350 mV.
[5] The tellurium separation and recovery method according to any one of [1] to [4] above, wherein the tellurium-containing raw material is copper telluride or reduced soot containing tellurium and selenium as main components.

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 2.5 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. In addition, 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 2.5 after leaching, tellurium oxychloride selectively precipitates in this pH range. Since selenium and silver are less likely to precipitate, tellurium can be separated from these impurities by filtration.

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 tellurium and copper. The graph which shows the relationship between pH and the dissolution amount of arsenic, selenium, and silver. The XRD diffraction chart of the starch produced by neutralization precipitation.

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%.

In the treatment method of the present invention, tellurium-containing raw materials are mixed with hydrochloric acid, and tellurium is oxidized and leached in the presence of an oxidizing agent, and the pH of the leachate containing tellurium is adjusted to 1.5 to 2.5 to obtain tellurium oxychloride. This tellurium separation and recovery method is characterized by precipitating and separating the precipitate to recover tellurium.

As the tellurium-containing raw material, for example, copper telluride or tellurium reducing soot is used. For example, copper telluride is obtained as a byproduct of the electrolytic refining of copper and contains about 50% of 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.

[Hydrochloric acid oxidation 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 is used as the tellurium-containing raw material, copper is leached together with tellurium. The initial concentration of the slurry is preferably in the range of 100 to 300 g / L. By this hydrochloric acid leaching, almost all of tellurium and copper in the raw material are leached.

If the initial concentration of the slurry is less than 100 g / L, the amount of liquid is too large, so that the optimum temperature cannot be maintained only by the heat of oxidation reaction, and heating is required. On the other hand, when the initial concentration of the slurry is higher than 300 g / L, the copper ion concentration becomes high and the oxidative leaching reaction becomes slow.

The initial hydrochloric acid concentration of the leaching slurry is preferably 4 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 the range where the redox potential (ORP) is 600 to 700 mV (Ag / AgCl electrode). When the ORP is less than 600 mV, tellurium is not sufficiently oxidized and leached, and when it is higher than 700 mV, the consumption of the oxidizing agent is increased, and the selenium is dissolved more and more.

The temperature of the leaching slurry is preferably 60 ° C to 90 ° C. When oxidative leaching is carried out in the range of the slurry concentration and hydrochloric acid concentration, the 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.

[Neutralization and precipitation process]
An alkali such as caustic soda is added to the leachate containing tellurium to adjust the pH of the leachate to 1.5 to 2.5 to precipitate the tellurium in the liquor. FIG. 3 and FIG. 4 show changes in these metal ion concentrations due to changes in pH of the hydrochloric acid leaching solution containing copper, arsenic, selenium, silver and the like together with tellurium. As shown in the figure, the tellurium concentration in the liquid gradually decreases and precipitates in proportion to the increase in pH. On the other hand, the copper concentration does not change, and the concentrations of arsenic, selenium, and silver do not change much up to around pH 2.

As shown in FIGS. 3 and 4, when the pH of the leachate is less than 1.5, tellurium having a concentration of several g / L is not preferable because it remains in the filtrate. On the other hand, when the pH of the leachate is higher than 2.5, selenium, arsenic and silver co-precipitate, so that the tellurium separability is lowered.

When the pH of the leachate is adjusted to 1.5 to 2.5, tellurium in the liquid precipitates, for example, by forming tellurium oxychloride as represented by the following formula [1]. On the other hand, since copper does not precipitate, tellurium and copper can be separated by solid-liquid separation. Further, even if arsenic, selenium, and silver are eluted from the raw material, they do not precipitate in the pH range, but tellurium is selectively precipitated, so that these impurity metals and tellurium can be separated.

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. This is because the solubility of tellurium oxychloride decreases with decreasing liquid temperature, as shown in FIG. In practice, it is preferable to start the neutralization treatment while the slurry temperature immediately after the hydrochloric acid oxidation leaching is higher than the normal temperature, because the labor required for reheating can be saved.
6H ₂ TeCl ₆ + 34NaOH → Te ₆ O ₁₁ Cl ₂ ↓ + 34NaCl + 23H ₂ O …… [1]

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. Copper, selenium, arsenic, silver, and the like are contained in the filtrate without being precipitated, so that tellurium and these impurity metals can be solid-liquid separated. 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), add a sulfiding agent to the alkaline solution to precipitate and separate the impurity metal in the liquid (sulfurized liquid treatment) The treated alkaline solution is made strongly acidic, a reducing agent is added, selenium in the solution is precipitated and separated at an oxidation-reduction potential of 350 mV or more (selenium reduction precipitation), and the reducing agent is added to the solution from which selenium has been removed. Metal tellurium is recovered by reducing and precipitating tellurium in the liquid at a potential of less than 350 mV (tellurium precipitation treatment).

Alkaline dissolution The tellurium oxychloride precipitate is dissolved with caustic soda. Copper, silver, etc. contained in a small amount in the precipitate remain as solids without dissolving. The liquid temperature may be from room temperature to about 60 ° C., and is preferably about pH 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.

Selenium reduction precipitation An acid is added to the purified alkali solution to make it strongly acidic. It is preferable to use 4 mol / L hydrochloric acid or the like. When a reducing agent (NaHSO ₃ or the like) is added to this strongly acidic liquid and the redox potential is adjusted to 350 mV or higher, preferably 350 mV to 360 mV, selenium in the liquid is reduced and deposited. To do. Tellurium remains in the liquid.

Tellurium reduction precipitation When a reducing agent (NaHSO ₃ or the like) is added to a solution from which selenium has been removed and adjusted to an oxidation-reduction potential of less than 350 mV, preferably less than 300 mV to less than 350 mV, tellurium in the liquid is reduced and deposited. The metal tellurium is recovered by filtration. The recovered metal tellurium can be washed with warm water, dehydrated and dried to obtain 3N purity metal tellurium.

Examples of the present invention will be described below.
[Example 1]
Copper telluride (Te: 44%, Cu: 40%) dry weight of 660 g was mixed with 2 L of hydrochloric acid aqueous solution (HCl: 6 mol / L ) to make a slurry, and heated to 40 ° C. Next, while observing the slurry temperature and oxidation-reduction potential, about 1 L of hydrogen peroxide solution (H ₂ O ₂ : 35%) (1.2 times equivalent to the amount necessary for the oxidation of Cu and Te) was added. The oxidation-reduction potential of the liquid 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 the slurry, about 90 ml of caustic soda solution (NaOH: 48%) 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. Over 90% of the copper in the raw material remains in the filtrate (filtrate 2.9 L, Cu: 82 g / L, Te: 1.5 g / L), while 98.5% of tellurium is contained in the precipitate ( table 1).

An XRD diffraction chart of the neutralized starch recovered in Example 1 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 1.

[Example 2]
750 g of tellurium oxychloride precipitate (water content 40%) was dissolved in caustic soda solution (2.4 L of 20% NaOH solution). 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 3
A precipitate formed by adding sodium hydrosulfide (NaHS) to the alkali solution (2.35 L) of Example 2 was separated by filtration. Hydrochloric acid was added to the sulfidized solution (2.3 L) to make it strongly acidic, sodium hydrogen sulfite (NaHSO ₃ ) was further added, and selenium was reduced and precipitated at an oxidation-reduction potential of 360 mV and separated by filtration. Furthermore, sodium bisulfite (NaHSO ₃ ) was added to the filtrate containing tellurium until the oxidation-reduction potential reached 300 mV, and tellurium was reduced and precipitated. The reduced tellurium was separated into solid and liquid, washed with warm water, dehydrated and dried to recover 270 g of metal tellurium having a purity of 3N (93% relative to tellurium in the raw material).

Example 4
Reduced soot (Te: 93%, Se: 3.8%) containing 200 g of dry weight containing tellurium and selenium was mixed with 2 L of a hydrochloric acid aqueous solution (HCl: 4 mol / L ) 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 (H ₂ O ₂ : 35%) (1.2 times equivalent to the amount required for oxidation of Te) 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 2). From Table 2, 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. In this alkaline solution, a tellurium concentration of 121 g / L (97.5% based on tellurium in the raw material) was present. On the other hand, only 63 ppm of selenium (1.3% with respect to selenium in the raw material) was dissolved.

Claims (5)

Tellurium-containing raw materials are mixed with hydrochloric acid, and tellurium is oxidatively leached in the presence of an oxidizing agent. The pH of the leachate containing tellurium is adjusted to 1.5 to 2.5 to precipitate tellurium oxychloride, and this precipitate is separated. Then, tellurium is recovered, and tellurium is separated and recovered.
The tellurium separation and recovery method according to claim 1, wherein in the oxidation leaching step, the initial slurry concentration of the tellurium-containing raw material is adjusted to 100 to 300 g / L, and the initial concentration of hydrochloric acid is adjusted to 4 to 6 mol / L.
The tellurium separation and recovery method according to claim 1 or 2, wherein the oxidation-reduction potential (Ag / AgCl electrode) is controlled to 600 to 700 mV in the oxidation leaching step.
Tellurium oxychloride is separated into solid and liquid and separated from the impurity metal in the filtrate. The recovered tellurium oxychloride is dissolved in alkali to separate the residue, and a sulfurizing agent is added to the alkaline solution to remove the impurity metal in the liquid. Precipitate and separate, make the purified alkali solution strongly acidic, add a reducing agent, precipitate selenium in the solution at an oxidation-reduction potential of 350 mV or more, separate it, and add the reducing agent to the solution from which selenium has been removed. In addition, the tellurium separation and recovery method according to any one of claims 1 to 3, wherein tellurium in the liquid is reduced and precipitated at an oxidation-reduction potential of less than 350 mV.
The method for separating and recovering tellurium according to any one of claims 1 to 4, wherein the tellurium-containing raw material is copper telluride or reduced soot containing tellurium and selenium as main components.

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