JP2000239753A - Method for separating and purifying tellurium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing inferior phase separation at co- extraction of impurity elements and back-extraction and recovering high grade metal tellurium by a simplified method using a solvent extraction process, from a tellurium-containing aqueous solution after use for treating copper electrolysis slime or the like. SOLUTION: Dibutyl carbitol is mixed with an aqueous solution which contains tellurium (IV) ions and (5 to 9) mol/l of chloride ions and in which >=3 mol/l of chloride ions, among the chloride ions, are in the form of hydrochloric acid, by which tellurium is selectively extracted. Subsequently, hydrochloric acid in an amount of (1.5 to 4) mol/l is mixed with an organic phase after the tellurium extraction, by which tellurium is back-extracted into aqueous phase. Then, a reducing agent such as sulfur dioxide is added to the aqueous solution after the back-extraction and reduction is effected to 280-300 mV to separate and recover metal tellurium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for separating tellurium from tellurium-containing substances such as copper electrolytic slime, and purifying the tellurium into high-purity metallic tellurium.

[0002]

2. Description of the Related Art The most typical raw material of tellurium (Te) is copper electrolytic slime, and tellurium is recovered by various methods using this as a raw material. Among them, the following two methods are known as typical methods that have already been industrially put into practical use: an alkali leaching method and a solvent extraction method.

The above alkaline leaching method is disclosed in US Bu.
r. Mines Inform. Circ. ", No. 8
569 (1973) and "Annual slime" or tellurium-containing material obtained by treating the same as described in "Japan Mining Association Autumn Meeting Proceedings J-11" (1984), pp. 41-43, etc. Is treated with an aqueous alkali solution or molten alkali under an oxidizing atmosphere, and leaching tellurium as water-soluble sodium tellurite.The leachate is purified by a precipitation method, and further reduced to metal tellurium by electrolysis or the like. Is the way.

The above-mentioned melt extraction method is described in "Tsvet
n. Metal ", No. 7 (1965), p74,
“Tsvetn. Metal. No. 27 (196)
7) As described in p22, etc., tellurium-containing substances are dissolved in sulfuric acid, hydrochloric acid, chlorine, etc., purified by a solvent extraction method, and then reduced with a reducing agent such as trioctylamine to reduce metal tellurium. How to get.

[0005]

Among the above-mentioned methods for recovering tellurium, in the alkali leaching method, it is difficult to completely oxidize all the tellurium in the raw material to tetravalent, so that the leaching rate of tellurium is low. In the case where a sodium compound is used as an alkali, some tellurium is precipitated as sparingly soluble sodium tellurate during the process, and the recovery rate is further reduced. For example, when copper electrolytic slime was dry-dissolved in alkali and the treated product was leached with sodium hydroxide, the leaching rate was only about 65%.

Furthermore, since various impurities soluble in alkali are present in the leaching solution obtained by the alkali leaching method, in order to purify tellurium efficiently, it is necessary to re-dissolve or re-precipitate tellurous acid. It is necessary to repeat various solid-liquid separation operations such as partial sulfurization, and the amount of used chemicals increases. Therefore, it cannot be said that the method is efficient and economical.

On the other hand, a recently developed solvent extraction method is a method for selectively extracting tellurium from a chloride aqueous solution using trioctylamine, tributyl phosphate or a quaternary ammonium salt as an extractant. Can be separated from selenium, which is difficult to completely separate by the precipitation method,
In addition, there is a characteristic that tellurium can be continuously separated, recovered, and purified.

However, when tellurium eluted in an acidic state such as acid dissolution or chlorine leaching is purified by a solvent extraction method, it can be separated from some elements such as selenium and alkali metals, but trioctylamine, tributyl phosphate, etc. In the case of an extractant such as a quaternary ammonium salt, since the co-extraction rate of other heavy metals, particularly the platinum group elements, increases, the impurity quality of metal tellurium finally recovered by reducing the back-extraction liquid increases, Further, there is a disadvantage that the loss of the platinum group element is large due to the incorporation into the tellurium metal.

Further, in these conventional extractants, tellurium is hardly back-extracted from the organic phase, so that it was necessary to back-extract using alkali hydroxide or a neutral aqueous ammonium chloride solution. However, in this case, when alkali hydroxide is used, co-extracted impurities precipitate and form a clad, and in an ammonium chloride aqueous solution, tellurium itself precipitates as a hardly soluble basic salt. Also in the case of the above, there is a problem that the phase separation becomes poor.

[0010] In addition, the concentration of impurities in copper electrolytic slime, which is a raw material for tellurium recovery, usually fluctuates greatly, so that the purification load at the time of extraction fluctuates. There is a possibility that the impurity level may fluctuate, but there has been no method to reliably cope with these fluctuations.

The present invention has been made in view of such a conventional situation,
When separating tellurium from a solution containing tellurium obtained by treating a raw material such as copper electrolytic slime by a solvent extraction method, co-extraction of various impurities including a platinum group element is prevented,
Also, it provides a method for purifying and recovering high-quality metallic tellurium with a small amount of impurities without causing phase separation failure due to precipitation of impurities or tellurium compounds at the time of back-extraction and capable of coping with fluctuations in raw material impurity levels. The purpose is to do.

[0012]

In order to achieve the above object, a method for separating and purifying tellurium provided by the present invention comprises:
(IV) Ion and 5 to 9 mol / l of chloride ions, of which 3 mol / l or more of the chloride ions are in the form of hydrochloric acid, mixed with dibutyl carbitol as an extractant, and selected for tellurium It is characteristically extracted.

In the method for separating and purifying tellurium of the present invention, the organic phase from which tellurium has been extracted as described above is mixed with 5 to 9 mo.
It is desirable to separate metal impurities into an aqueous phase by washing with 1 / l hydrochloric acid. Further, 1.5 to 4 mol / l hydrochloric acid is mixed with the organic phase from which tellurium has been extracted or the organic phase which has been washed with hydrochloric acid as described above, and tellurium is back-extracted into the aqueous phase.

Further, the method for separating and purifying tellurium of the present invention is characterized in that a reducing agent is added to the above-mentioned aqueous solution containing tellurium which is back-extracted, and tellurium is reduced to separate and collect metallic tellurium. As the reducing agent to be used, sulfur dioxide is preferable. At the time of this reduction, preferably, the back extract is reduced to a potential of 370 to 420 mV with respect to a silver-silver chloride electrode, and a mother liquor obtained by separating a formed precipitate is subjected to 280 to 30 mV.
The metal tellurium is recovered by reducing again to 0 mV.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a solvent extraction method similar to the conventional one is used as a method for separating tellurium, but dibutyl carbitol is used as an extractant. By using dibutyl carbitol, which is a neutral ether extractant, as an extractant, most of these impurities are distributed to the aqueous phase even in the presence of impurities such as platinum group elements that are easily co-extracted with tellurium. In addition, tellurium can be selectively extracted into the organic phase.

Furthermore, by extracting tellurium with dibutyl carbitol, the tellurium extracted into the organic phase is likely to be distributed in the aqueous phase when the concentration of hydrochloric acid is reduced. Therefore, this property is used to separate tellurium from impurities. Purify. Further, utilizing the fact that the potential at which the coexisting impurity element is reduced to elemental elements is different from that of tellurium, high-quality tellurium with few impurities can be recovered by reduction at a controlled potential.

The method of the present invention will be described in detail for each step according to the flowchart shown in FIG. First, in a raw material dissolving and leaching step, a raw material such as tellurium-containing copper electrolytic slime is dissolved using various strong acids such as hydrochloric acid, sulfuric acid, and nitric acid. The raw material is sulfide, selenide,
In the case of containing a compound which is hardly soluble directly in an acid such as telluride, it is necessary to leaching with an oxidizing agent such as chlorine. As the type of acid used, hydrohalic acid is most desirable from the viewpoints of solubility of tellurium salt, ease of hydrolysis, lipophilicity of the salt, etc. Most suitable.

In the next extraction step, the valence of tellurium that can be extracted with dibutyl carbitol is tetravalent. If the raw material has been treated with alkali or the concentration of free hydrochloric acid during chloride dissolution is very low, some tellurium may be present as hexavalent ions, but halogens other than hydrofluoric acid may be present. When heated in hydrofluoric acid, the entire amount can be easily reduced to tetravalent. An example of the reduction reaction of tellurium (VI) ion to tellurium (IV) ion in the presence of hydrochloric acid is shown in the following chemical formula 1.

[0019]

Embedded image Na ₂ TeO ₄ + 8HCl → TeCl ₄ + Cl ₂
+ 4H ₂ O + 2NaCl

Further, when chlorine is leached from a mixture containing metal tellurium, selenium, etc., hydrochloric acid is generated during the reaction, so that the total amount of tellurium can be obtained in tetravalent by adjusting the slurry concentration at the time of leaching. Furthermore, after the end of the dissolution and leaching step, a small amount of a reducing agent is added, or metals, sulfides,
When reducing substances such as selenide and telluride are present, by adding a small amount of the raw material to the leachate,
Tellurium can be surely made tetravalent. The valence of tellurium in the extract can be known from the oxidation-reduction potential, and the potential of the liquid is 800 mV with respect to the silver / silver chloride electrode.
Below, the total amount of tellurium exists as tetravalent.

The reason for using dibutyl carbitol as an extractant in the tellurium extraction step of the present invention is as follows. That is, it is considered that the form of tellurium in the hydrochloric acid acidic solution exists as chloro complex salt ions or tellurium chloride molecules. The former can be extracted with an anion-exchange type extractant such as trioctylamine which has been conventionally used, and the latter can be extracted with a neutral extractant.However, the form of tellurium in the aqueous phase is actually Since the two can be freely interchanged, quantitative extraction is possible using any of the extractants.

However, regarding the separability from other elements,
In an anion-exchange-type extractant, most of the ions that form anions in hydrochloric acid are co-extracted, and the tellurium salts formed in the organic phase are often very stable,
Difficult to decompose due to back extraction. In contrast, with the neutral extractant, most of the impurities such as the platinum group elements that are easily co-extracted with tellurium are distributed to the aqueous phase, and it is possible to selectively extract tellurium into the organic phase and extract the tellurium. Tellurium can be back-extracted into the aqueous phase simply by lowering the hydrochloric acid concentration.

Further, among the neutral extractants, carbon, hydrogen,
Compounds containing elements other than oxygen, such as alkyl phosphates and similar compounds, have a strong solvating ability of the extracted species, form polymers in the organic phase, and may be less difficult to back-extract than amines. Therefore, a neutral extractant which does not have such a problem and is composed only of carbon, hydrogen and oxygen having low basicity of the solvation site of the extracted species is preferable. Also, when comparing neutral extractants consisting only of carbon, hydrogen, and oxygen, compounds having lower molecular weights have higher water solubility, flammability, and odor, so ethers, esters, ketones, and the like having a molecular weight of several hundreds are desirable. . For the above reasons, in the present invention, dibutyl carbitol, which is a higher ether, was selected as the optimal extractant.

The extraction reaction of the present invention is accelerated as the concentration of hydrochloric acid and the concentration of chloride ions in the aqueous solution increase. When there is almost no chloride other than hydrochloric acid, the phase ratio O / A = 1
/ 1, the tellurium extraction rate is 78% at a hydrochloric acid concentration of 3 mol / l, and the tellurium extraction rate is 90% at a hydrochloric acid concentration of 5 mol / l.
It is. However, when the hydrochloric acid concentration is 9.5 mol / l or more, the mutual solubility between the organic phase and the aqueous phase is significantly increased, and the extraction operation itself becomes difficult. Therefore, the hydrochloric acid concentration of the aqueous solution is preferably 3 to 9.5 mol / l, and 5 to 9 m / l.
The range of ol / l is more preferred.

Actually, an aqueous solution obtained by dissolving and leaching copper electrolytic slime or the like contains chloride ions other than hydrochloric acid, and the presence of chloride ion concentrations other than hydrochloric acid increases the tellurium extraction rate. To obtain the same extraction rate, the higher the concentration of the coexisting chloride ions, the lower the hydrochloric acid concentration. However, even if the total chloride ion concentration rises to the saturation concentration, that is, up to about 9 mol / l, if the hydrochloric acid concentration in the concentration falls below 3 mol / l, quantitative extraction of tellurium becomes difficult even in multiple stages. . On the other hand, when the hydrochloric acid concentration is fixed at 3 mol / l, the total chloride ion concentration at which tellurium can be extracted almost quantitatively is 5 to 9 mol / l.

For the above reasons, in the extraction step of the present invention, the hydrochloric acid concentration of the aqueous solution is 3 mol / l or more, and the total chloride ion concentration is 5 to 9 mol / l. Even if the hydrochloric acid concentration and the chloride ion concentration are lower than the above, extraction is possible in principle, but it requires a large number of extraction stages, and it is difficult to implement it economically. Practically, it is preferable that 95% or more of tellurium can be extracted under the conditions of a phase ratio O / A = 1/1 and about three extraction stages.
It is particularly desirable that the concentration be 1 / l or more and the total chloride concentration be 8 to 9 mol / l.

The phase ratio at the time of extraction must be determined in consideration of the amount of tellurium that can be extracted from the organic phase. The loading of tellurium on the organic phase depends on the concentration of hydrochloric acid and the concentration of chloride ions, but up to about 85 g / l can be extracted under optimal conditions.

As described above, tellurium extracted into the organic phase is back-extracted from the organic phase to the aqueous phase. However, since the organic phase contains impurities such as platinum group elements extracted together with tellurium,
Prior to the back extraction step, it is preferable to selectively separate impurities into an aqueous phase by washing with hydrochloric acid. In this impurity washing step, in order to prevent tellurium from being back-extracted into the aqueous phase, hydrochloric acid having almost the same concentration as the aqueous solution at the time of extraction, or a mixture of chloride and hydrochloric acid that does not affect the purification of tellurium is used. Is preferred. In general, among chlorides, hydrochloric acid is the cheapest in terms of unit price per mole, so that it is most advantageous to use an aqueous solution of hydrochloric acid alone. In this case, the concentration of hydrochloric acid is 5 to 9 mol so as to prevent back extraction of tellurium and mutual dissolution of hydrochloric acid and tellurium.
/ L concentration range is preferred.

Next, in the step of back-extraction of tellurium from the organic phase, the chloride ion concentration and the hydrochloric acid concentration in the aqueous phase must be lower than the level at which tellurium can be extracted.
Use hydrochloric acid with a concentration of not more than ol / l. However, when the hydrochloric acid concentration is reduced to less than 1.5 mol / l, tellurium may be hydrolyzed and a basic salt may be precipitated. Therefore, the hydrochloric acid concentration needs to be 1.5 mol / l or more.
The particularly preferred concentration of hydrochloric acid is 2.5 to 3.0 mol / l.
It is. In addition, impurities that are more easily hydrolyzed than tellurium,
For example, when a large amount of antimony and the like coexist, it is possible to promote the chloro complexation by adding about 0.3 mol / l of a chloride other than hydrochloric acid to the back-extraction solution, thereby preventing the formation of a precipitate due to hydrolysis. It is.

Most of the impurity elements accompanying tellurium can be separated by the above-mentioned back-extraction step, but a small amount of impurities still exist together with tellurium in the back-extraction solution. Among these impurities, impurity elements such as gold and selenium, which are more easily reduced than tellurium, can be precipitated by an impurity reduction step of weakly reducing the back extract, and can be easily removed by solid-liquid separation.

H ₂ SeO ₃ / Se between AuCl ₄ / Au
Since the standard oxidation-reduction potentials between TiO ₂ and TeO ₂ / Te are 1.002 V, 0.740 V, and 0.521 V, respectively, in principle, 321 to 5 with respect to the silver / silver chloride electrode.
There is a possibility that impurities such as gold and selenium can be separated by a reduction of 40 mV, but in the actual impurity reduction step, 370 to 4
The range of 20 mV is optimal. If the potential is lower than 370 mV, tellurium is co-reduced with the impurity element, so that tellurium is lost. Conversely, if the potential is higher than 420 mV, reduction of the impurity element becomes incomplete, and the quality of the finally recovered tellurium is reduced. It is because it falls. The reduction potential of the liquid can be adjusted by electrolysis. However, coexistence of an impurity element such as copper which easily forms telluride is not preferable because co-reduction of tellurium is caused depending on conditions.

As the reducing agent to be used, any reducing agent which can be adjusted to the above-mentioned potential can be used without any limitation. However, the stability of the potential at the end point, the reaction speed, the prevention of tellurium contamination, and the like.
Sulfur dioxide is the most suitable in consideration of prevention of local potential drop and economics. The higher the reduction temperature, the faster the reaction rate, but heating is not an essential condition. Further, the time for maintaining the reduction potential varies depending on the liquid composition, the supply speed of the reducing agent, the reduction temperature, the presence or absence of nuclei, the concentration of nuclei, and many other factors. However, in general, the reduction of impurity elements such as selenium tends to be incomplete in less than 5 minutes, and the co-precipitation amount of tellurium increases to around 10% even if the potential is adjusted more than 2 hours. A reduction in about 60 minutes often gives good results.

In the impurity reduction step (first-stage reduction), when both selenium and tellurium are tetravalent, the higher the reduction rate and the higher the precipitation rate of tellurium, the later the tellurium reduction step (second Selenium in tellurium can be prevented by step reduction). However, in practice, often irreducible 6
Since selenium is present and has a low reduction rate and precipitates at the end, when the reduction rate of the first-stage reduction is increased, the selenium grade in tellurium in the second-stage reduction is rather lowered in many cases.

The mother liquor from which the impurity elements have been removed by precipitation in the impurity reduction step can selectively recover only tellurium as metallic tellurium by the second stage reduction in the next tellurium reduction step. That is, the oxidation-reduction potential of the mother liquor is 28
By reducing to 0 to 300 mV, the entire amount of tellurium is reduced and precipitates as metallic tellurium, but heavy metal elements having a lower reduction potential such as antimony, copper, bismuth, and nickel as coexisting impurities are not reduced. Therefore, high-quality metallic tellurium can be recovered by solid-liquid separation.

Also in this tellurium reduction step, sulfur dioxide is optimal as a reducing agent. Other weak reducing agents can be used, but if the mother liquor contains impurities that easily produce telluride, it is not preferable because it tends to bend easily and it becomes difficult to recover highly pure metal tellurium. Further, in the tellurium reduction step, the potential does not drop below the above-mentioned optimum value without performing any potential control, and only tellurium is selectively reduced.

[0036]

Example 1 Using a hydroxide containing each element shown in Table 1 below, hydrochloric acid and sodium chloride, the same elemental composition (g / g) was used as shown in Table 1.
l) and the concentration of hydrochloric acid and chloride ions (mol /
l) Two kinds of stock solutions 1 and 2 differing only in (1) were prepared. In addition, Table 1 is divided into Table 1-1 and Table 1-2, and represents the entire Table 1 together (same as the following table).

[0037]

[Table 1-1] Composition of stock solution (g / l) Sample Cl concentration HCl concentration Sb Fe Se Te As Pt stock solution 1 4 2.9 2.6 10.2 2.03 6.69 1.79 17.6 Stock solution 2 7 6.6 2.6 10.2 2.03 6.69 1.79 17.6

[Table 1-2] Composition of stock solution (g / l) Sample Pd Rh Au Ir Ir Os Ru Bi Stock solution 1 11.4 7.81 10.1 0.48 0.53 0.64 2.75 Stock solution 2 11.4 7.81 10.1 0.48 0.53 0.64 2.75

After each of the above stock solutions was mixed with dibutyl carbitol as an extractant for 10 minutes at a phase ratio of O / A = 1/1, the elements contained in the obtained organic phase and aqueous phase were analyzed. The composition (g / l) of each element obtained is shown in Table 2 below.

[0039]

[Table 2-1] Composition of aqueous phase and organic phase (g / l) Sample Sb Fe Se Te As Pt stock solution 1 / water phase 2.09 5.64 0.64 6.16 1.66 13.8 Stock solution 1 / organic phase 0.011 3.80 <0.005 0.010 0.047 0.069 Stock solution 2 / water phase 0.019 0.008 2.33 0.33 1.65 17.3 Stock solution 2 / organic phase 0.79 10.5 0.13 5.80 0.32 1.3

[Table 2-2] Composition of aqueous phase and organic phase (g / l) Sample Pd Rh Au Ir Ir Os Ru Bi stock solution 1 / water phase 9.85 7.35 0.041 0.53 0.30 0.41 2.61 Stock solution 1 / organic phase 0.011 <0.005 9.9 <0.005 0.060 0.039 <0.005 Stock solution 2 / water phase 10.9 8.18 <0.005 0.54 0.40 0.53 2.91 Stock solution 2 / organic phase 0.19 <0.005 10.7 0.068 0.048 0.10 0.019

From these results, it can be seen that the extraction ratio of tellurium into the organic phase greatly varies depending on the chloride ion concentration and the hydrochloric acid concentration of the aqueous solution. In addition, among the coexisting elements, platinum group elements, selenium, arsenic, and bismuth always show lower values than tellurium, but antimony and iron are coextracted with tellurium.

Example 2 The composition (g / l) shown in Table 3 below has a chloride ion concentration of 8.4 mol / l and a hydrochloric acid concentration of 6.75 mol / l.
Was prepared. Dibutycarbitol was mixed with 680 ml of this stock solution at a phase ratio of O / A = 1/1. The aqueous phase as the raffinate was further extracted twice with fresh dibutyl carbitol. The composition (g / l) of each of the three raffinate solutions and the organic phase of the first extraction is shown in Table 4 below.

[0042]

Table 3 Composition of stock solution (g / l) Se Te Au Ag Cu Pb As Bi Sb Fe 9.33 50.1 0.004 0.63 18.5 7.22 0.28 13.8 0.87 0.38

[0043]

[Table 4-1] Composition of aqueous phase and organic phase (g / l) Extracted sample liquid volume (ml) Se Te Au Ag Cu Once aqueous phase 620 8.62 2.41 <0.001 0.63 20.0 Twice aqueous phase 540 8.17 0.32 <0.001 0.66 20.5 3 times aqueous phase 540 8.10 0.048 <0.001 0.67 20.2 1 time organic phase 715 0.906 37.4 <0.005 0.004 0.14

[Table 4-2]

As can be seen from the results in Table 4, a single extraction with dibutyl carbitol resulted in 99.92% tellurium.
Although extracted, silver, copper, arsenic, and bismuth among the impurity elements were hardly extracted, and selenium was slightly extracted. However, antimony and iron were extracted with tellurium.

Next, the organic phase of the single extraction shown in Table 4 above was combined with 1.5 to 7.0 mol / l hydrochloric acid and the phase ratio O / A = 1 /.
1 and the distribution of tellurium and impurity elements into the aqueous phase was examined. As a result, selenium, silver, copper, lead, arsenic, and bismuth were completely back-extracted into the aqueous phase irrespective of the hydrochloric acid concentration, so that the concentrations of tellurium, antimony, and iron dissolved in the aqueous phase (g
/ L) is shown in Table 5 below. The hydrochloric acid concentration was 1.5.
In the case of mol / l, a slight amount of hydrolyzate was observed.

[0046]

[Table 5]

As can be seen from the above results, the phase ratio O / A
In the case of = 1/1, a hydrochloric acid concentration of 5 mol / l or more is required to suppress the loss of tellurium to the aqueous phase during scrubbing to 10% or less. Also, at the time of back extraction, the lower the concentration of hydrochloric acid, the greater the distribution of tellurium in the aqueous phase, but in order to completely prevent hydrolysis, the concentration of hydrochloric acid is preferably at least 2.5 mol / l.

As compared with Example 1, the distribution of tellurium to the organic phase was generally higher in Example 2 under similar conditions. This is because elements co-extracted with tellurium coexist at a high concentration, thereby suppressing tellurium extraction.

Example 3 Using a stock solution having the composition (g / l) shown in Table 6 below, three extraction steps with dibutyl carbitol, and a scrubbing step with hydrochloric acid 5
A batch simulation was carried out assuming multistage countercurrent extraction in which the phase ratio of the stage and the extraction stage was O / A = 1/2 and the phase ratio of the scrubbing stage was O / A = 1/1. The hydrochloric acid concentration of the stock solution was 7.7.
mol / l, and the chloride ion concentration is 9.3 mol / l.
l.

[0050]

Table 6 Composition of stock solution (g / l) Se Te Au Ag Cu Rh Rh Pb As Bi Sb Fe 12 92 0.027 0.52 54 0.13 6.5 0.5 32 1.9 1.1

The method of operation is as shown in FIG. 2. In the figure, "stock solution" is 50 ml of stock solution, "DBC" is 50 ml of dibutyl carbitol as an extractant, and "wash solution" is 7 ml.
The arrows pointing to the lower right indicate the flow of the organic phase, and the arrows pointing to the lower left and right below indicate the flow of the aqueous phase.

In the figure, the mark 印 represents the mixing operation for 10 minutes, and ~ corresponds to the first to third stages of extraction, respectively.
'~' Corresponds to 1 to 5 stages of scrubbing, respectively. The analysis sample of each stage was collected after each operation of ~ and '~'. Table 7 shows the composition (g / l) of the aqueous phase in each stage, the composition (g / l) of the organic phase in each stage in Table 8, and the final extraction in Table 9 as the analysis results of the collected samples. The distribution (%) of each element between the residual liquid and the extracted organic phase is shown.

[0053]

Table 7 aqueous phase composition of each stage (g / l) aqueous solution volume (ml) Cu Se Sb Fe Te extractions 3 stages 45.0 31 6.7 0.027 <0.005 0.57 extractions second stage 44.0 31 7.0 0.027 <0.005 1.8 extract Out 1st stage 44.0 31 6.6 0.034 <0.005 9.4 Scratch 1st 23.0 0.79 0.69 <0.005 <0.005 5.1 Scratch 2nd 24.5 0.044 0.020 0.040 <0.005 3.1 Scrunch 3rd 24.5 0.007 0.009 <0.005 <0.005 2.4 5 <8 86.0 0.005 <0.005 1.8 Scramble 5 steps 25.5 <0.005 0.006 <0.005 <0.005 1.7

[0054]

TABLE 8 organic phase composition (g / l) organic phase liquid volume (ml) Cu Se Sb Fe Te extractions 3 stages 25.0 0.12 0.30 0.027 0.013 3.56 extractions two stages 25.5 0.20 0.38 0.015 0.006 18.5 out extraction of each stage 1 stage 29.0 0.31 0.39 1.62 0.99 84.3 Scramble 1 stage 29.0 0.026 0.27 1.62 0.99 80.5 Scramble 2 stages 29.5 0.005 0.21 1.53 1.02 78.5 Scrunch 3 stages 30.5 <0.005 0.18 1.56 0.95 76.0 Scrunch 4 stages 31.0 <0.95 0.17 <0.005 0.16 1.55 0.96 74.4

[0055]

[Table 9] Partition ratio (%) to the final raffinate and the extracted organic phase Cu Se Sb Fe Te extraction 3 step aqueous phase 99.99 98.4 2.51 0.76 1.12 Scraping 5 step organic phase 0.01 1.59 97.5 99.2 98.9

From the results, after three extraction steps and five scrubbing steps, 92 g / l of tellurium in the stock solution was reduced to 0.57 g / l in a state of being diluted twice with the scrubbing liquid, and It can be seen that 98.9% was extracted. On the other hand, copper, which is a major impurity element, is 99.9%.
It was confirmed that 9% and 98.4% of selenium remained in the aqueous phase. However, antimony and iron present in small amounts behaved almost the same as tellurium and were co-extracted with tellurium into the organic phase.

Example 4 An organic phase extracted with dibutyl carbitol having the composition (g / l) shown in Table 10 below was used as a stock solution and 3 mol /
A batch simulation was carried out assuming three stages of back extraction with 1 l hydrochloric acid and a multistage countercurrent extraction with a phase ratio of O / A = 1/2.

[0058]

Table 10 Composition of extracted organic phase (g / l) Se Sb Fe Te 0.21 1.53 0.92 58.9

The operation method is as shown in FIG. 3. In FIG. 3, "extracted organic" refers to 30 ml of the organic phase extracted with dibutyl carbitol in Table 10, and "3H HCl" refers to 3 mol / l.
The arrow toward the lower right indicates the flow of the organic phase and the arrow toward the lower left indicates the flow of the aqueous phase. Also,
The circles represent these mixing operations for 10 minutes, and the mixing operations of ~ correspond to the first to third stages in the multi-stage countercurrent extraction, respectively.

The analytical sample of each stage was collected after each of the above operations, and the composition (g / l) of the back extraction liquid (aqueous phase) of each stage is shown in Table 11 below as the analysis result of each sample. 12 shows the composition (g / l) of the organic phase after back extraction in each stage, and Table 13
Of each element to the final back-extraction solution and back-extraction organic phase (%)
showed that.

[0061]

[Table 11] Composition of back-extraction solution in each stage (g / l) Volume of back-extraction solution (ml) Se Sb Fe Te Back-extraction 1 stage 33.0 0.071 0.26 0.11 26 Back-extraction 2 stage 31.7 0.034 0.17 0.32 24 Back-extraction 3 stage 30.3 0.029 0.18 0.46 10

[0062]

Table 12 Organic phase composition of each stage (g / l) organic phase liquid volume (ml) Se Sb Fe Te stripping 1 stage 14.0 0.13 1.31 1.03 54.1 back extracted two stages 13.4 0.13 1.23 1.03 27.3 back extracted three stages 13.0 0.09 0.96 0.42 5.46

[0063]

[Table 13] Partition ratio (%) to the final back-extract and the organic phase after extraction Se Sb Fe Te Back-extraction one-stage back-extraction 67.4 40.71 39.96 92.4 Organic phase after three-stage back-extraction 32.6 59.3 60.1 7.6

As described above, 92% or more of tellurium could be back-extracted into the aqueous phase at a concentration of 26 g / l by three-stage back-extraction.
Since selenium has already been separated in the scrubbing stage as in Example 3 above, the back extraction rate is a low value in terms of calculation, but it was actually back extracted to the order of 0.0 ng / l. At this time, the grade of the back extraction liquid in the back extraction 1 stage is T
e / (Te + Se + Sb + Fe) = 0.983.

On the other hand, antimony and iron were likely to remain in the organic phase even after back-extraction, but the organic phase after the final tellurium extraction was washed with a 0.2 mol / l aqueous sodium bisulfite solution. Antimony, iron and tellurium could be completely back-extracted to less than 0.005 g / l.

Example 5 A continuous tellurium recovery test was carried out using an extraction apparatus (mixer settler) as shown in FIG. 4 with three extraction stages, five scrubbing stages, and three back extraction stages. In FIG. 4, a rectangular part with a circle is a mixer 1 for mixing an organic phase and an aqueous phase, a rectangular part without a circle is a settler 2 for phase separation of an organic phase and an aqueous phase, and the aqueous phase is a solid arrow. Direction and the organic phase flows in the direction of the dashed arrow.

That is, tellurium in the stock solution is extracted with dibutyl carbitol (DBC) through three extraction stages, and the aqueous phase with reduced tellurium grade is finally released as a raffinate. The organic phase from which tellurium has been extracted is washed with hydrochloric acid in five scrubbing stages and the main impurities are released into the aqueous phase. The purified organic phase is sent to three back extraction stages, and tellurium is recovered in the aqueous phase. The organic phase after tellurium back-extraction is fed again to the third stage of the extraction stage.

Using this mixer settler, the following Table 14
Tellurium was continuously recovered from a stock solution having a composition shown in Table 2 below, a hydrochloric acid concentration of 5.3 mol / l, a chloride ion concentration of 8.2 mol / l, and a potential of 620 mV with respect to a silver / silver chloride electrode.
The actual operating conditions are shown in Table 15 below.

[0069]

Table 14 Composition of stock solution (g / l) Se Te Au Ag Cu Rh Rh Pb Bi Sb 16.6 59.0 0.01 0.41 65.6 0.23 7.41 23.2 0.52

[0070]

[Table 15] Charged liquid phase Specific residence time (min) Operation (ml / min) (O / A) Mixer settler extraction stage Stock solution: 40 DBC: 40 1/2 25 25 Scrubbing stage 7mol / l HCl: 40 1/1 7.5 37.5 Reverse extraction stage 3mol / l HCl + 2% NaCl: 80 1/2 5 25

The samples were operated continuously for 44 hours under the above conditions, and the average samples of the collected organic phase and aqueous phase were analyzed. The results of investigating the distribution (%) of each element are shown in Table 16 below. The gold and antimony remaining at a low concentration in the back-extraction organic phase could be back-extracted to less than 0.005 g / l by treating with sodium hydrogen sulfite aqueous solution in the same manner as in Example 4.

[0072]

[Table 16] Partition ratio (%) of each element Se Te Au Ag Cu Rh Rh Pb Bi Sb extraction liquid 99.7 5.1 0 100 100 100 100 100 9.6 Reverse extraction liquid 0.3 94.8 0 0 0 0 0 0 59.5 Reverse extraction organic phase 0.0 0.1 100 0 0 0 0 0 30.9

Example 6 610 ml of the tellurium back-extracted solution shown in Table 17 below was divided into three portions, each of which was heated to 90 ° C., and brought to a potential (a value for a silver / silver chloride electrode) shown in Table 18 below using sulfur dioxide. 2
After maintaining for 0 minutes, the first-stage reduction was performed, and the formed precipitate was separated. Thereafter, a precipitate of metallic tellurium was obtained by a second-stage reduction in which the filtrate was reduced to the minimum potential (284 mV).

[0074]

Table 17 Composition of stock solution (g / l) Se Te Au Ag Cu Pb As Bi Sb Fe 0.009 33.9 <0.001 <0.001 <0.001 <0.005 <0.01 <0.005 0.162 0.322

Table 18 below shows, together with the first-stage reduction potential (mV), the tellurium precipitation rate (%) in the first-stage reduction precipitation corresponding to the loss during the reduction purification of tellurium, and the recovery in the second-stage reduction. The selenium concentration (ppm) in the tellurium metal was shown. These results indicate that adjusting the potentials in the first and second reduction stages can minimize tellurium loss and prevent the incorporation of selenium into tellurium metal.

[0076]

[Table 18]

When the first-stage reduction was carried out at 377 mV and the filtrate from which the precipitate was separated was further reduced to 284 mV in the second stage, the grade (ppm) of the obtained metallic tellurium is shown in Table 19 below. Impurity elements such as selenium, antimony, and iron that could not be completely separated only by the extraction process
Almost completely separated by the reduction treatment of the stage.

[0078]

[Table 19] of metallic tellurium quality (ppm) Na Mg Fe Ni Cu Se Ag Al Si Sb Au Bi 0.08 0.1 0.9 0.1 0.4 12 4.3 0.5 1.8 0.8 0.4 0.9

Example 7 Purification of tellurium by reduction using 150 liters of a back extract obtained in the same manner as in the mixer settler test of Example 5 and having the composition (g / l) shown in Table 20 below And recovery was carried out.

[0080]

Table 20 Composition of back-extraction solution (g / l) Au Ag Pb Cu Se Sb Te <0.01 <0.01 <0.01 <0.01 <0.01 0.57 22.9

First, the temperature of the above-mentioned back-extraction solution was raised to 90 ° C., and sulfur dioxide was blown into the solution while stirring to reduce the potential to 3 ° C.
The first-stage reduction was performed until the voltage became 90 mV. After filtering the formed precipitate, the filtrate was heated to 90 ° C. and reduced to 290 mV by blowing in sulfur dioxide while stirring again.
The metallic tellurium produced in the second-stage reduction was recovered, washed with water and dried, and the composition was analyzed. The results are shown in Table 21 below.

[0082]

[Table 21] Grade of metallic tellurium (ppm) Na Mg Fe Ni Cu Se Ag Sb <1 <1 <1 <1 <5 <14 <1

From the comparison with Example 6, it was found that in Example 7, reduction was made uniform by increasing the treatment amount, and impurity quality was rather lowered. In addition, 3.5% of tellurium in the back extract was reduced in the first stage, and the remaining 96.5 was reduced.
% Precipitated in the second stage reduction. Tellurium in the final mother liquor is 0.
It was less than 01 g / l.

[0084]

According to the present invention, tellurium can be selectively extracted and separated by dibutyl carbitol, regardless of the type and amount of impurities in the raw material, and further, this can be back-extracted and reduced to remove impurities. A small amount of high-grade metallic tellurium can be recovered. Moreover, continuous separation and purification of tellurium is possible, and there is no loss of platinum group elements contained in raw materials such as copper electrolytic slime, so that the industrial merit is great.

[Brief description of the drawings]

FIG. 1 is a flowchart showing each step of the method of the present invention.

FIG. 2 is an operation diagram of a batch simulation assuming a multistage countercurrent extraction of three stages of extraction and five stages of scrubbing in Example 3.

FIG. 3 is an operation diagram of a batch simulation assuming multistage countercurrent extraction of three stages of back extraction in a fourth embodiment.

FIG. 4 is a conceptual diagram for explaining a mixer settler used for extracting and purifying tellurium in Example 5.

[Explanation of symbols]

 1 mixer 2 settler

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yuji Kurokawa 3-5-3 Nishiharacho, Niihama-shi, Ehime F-term in the Besshi Works of Sumitomo Metal Mining Co., Ltd. 4K001 AA26 BA17 CA07 DB04 DB11 DB17 DB21 DB26 HA12

Claims (6)

[Claims] Claims: 1. A tellurium (IV) ion and 5 to 9 mol / l
Of chloride ions, of which 3 mol
A method for separating and purifying tellurium, comprising mixing dibutyl carbitol as an extractant with an aqueous solution in which at least 1 / l is in the form of hydrochloric acid, and selectively extracting tellurium. 2. The organic phase from which tellurium has been extracted is 5 to 9 mol.
2. The method for separating and purifying tellurium according to claim 1, wherein metal impurities are separated into an aqueous phase by washing with hydrochloric acid. 3. The organic phase from which tellurium has been extracted has a thickness of 1.5 to 4 m.
3. The method for separating and purifying tellurium according to claim 1, wherein ol / l hydrochloric acid is mixed and tellurium is back-extracted into an aqueous phase. 4. The separation and purification of tellurium according to claim 3, wherein a reducing agent is added to the aqueous solution containing tellurium back-extracted from the organic phase, and tellurium is reduced to separate and recover metallic tellurium. Method. 5. The method for separating and purifying tellurium according to claim 4, wherein sulfur dioxide is used as a reducing agent. 6. A back extraction solution is applied to a silver-silver chloride electrode at 370 to
5. The metal tellurium is recovered by reducing to a potential of 420 mV and reducing the mother liquor from which a formed precipitate is separated again to 280 to 300 mV.
Or the method for separating and purifying tellurium according to 5.