JPH0713313B2 - Tellurium recovery method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for recovering tellurium as copper telluride from a tellurium-containing liquid such as a leachate of copper electrolytic slime.

[Prior Art and Problems] In copper smelting, ore is usually smelted in a reverberatory furnace, a converter, a refining furnace or the like to produce crude copper or purified copper, which is further electrolyzed to produce electrolytic copper having a purity of about 99.99%. Is getting By this electrolytic refining, arsenic, selenium, tellurium, platinum, palladium,
Valuable metals such as gold and silver are contained in raw slime and extracted from the electrolytic cell. The valuable metal is contained in the raw slime to the extent shown in the following table.

In order to recover these valuable metals, raw slime is leached with sulfuric acid, leach slime containing gold and silver is sent to these recovery processes, while leachate containing residual valuable metals is sent to the decoppering electrolysis process. To be Impurities such as arsenic are removed in the copper removal electrolytic process. The decoppered slime generated by the decopperization is sent to the smelting step, and the tail solution is sent to the raw slime leaching step and mixed with the leaching solution.

Conventionally, as methods for removing and recovering tellurium from the exudate of the raw slime, (a) a method of adding copper powder and (b) a method of electrolysis are known.

(A) As a method of adding copper powder, metallic copper is added to a tellurium-containing liquid, stirred at a temperature of about 60 to 80 ° C., and reacted on the metallic copper surface to obtain copper telluride.

(B) In the electrolysis method, an insoluble anode is used to electrolytically collect copper and the like, and at the same time, tellurium in the liquid is electrodeposited as copper telluride.

However, since the copper powder is expensive, the method (a) is not suitable for practical use, and it is difficult to reduce the concentration of tellurium in the leachate to 1 g / or less by the method (b). There is a low problem.

[Means for Solving Problems] The present inventor has attempted to improve a method for recovering tellurium by electrolysis, and if copper is used for an electrode and electrolysis is performed by an alternating current, tellurium is deposited as copper telluride and effectively and easily separated. We obtained the knowledge that can be collected.

[Configuration of the Invention] According to the present invention, there is provided a tellurium recovery method for recovering copper telluride by electrolyzing a tellurium-containing liquid using a copper electrode and alternating current to deposit copper telluride.

As a liquid containing tellurium, a sulfuric acid leaching solution of raw slime produced by copper electrolytic refining can be used. PH of the leachate
Is around 0, and TeO ₅ , H ₃ AsO ₅ contained in raw slime
Exists in the liquid in the form of HTeO ₂ ⁺ and As ⁵⁺ .

In addition to the sulfuric acid leachate, nitric acid leachate, leachate obtained by adding hydrochloric acid to sulfuric acid, or the like may be used. The addition of hydrochloric acid improves the electrolysis rate. By adding a reducing agent such as phosphorous acid or hypophosphorous acid in place of hydrochloric acid or in combination with hydrochloric acid, the electrolysis rate or tellurium recovery rate can be improved.

When a copper electrode is charged into the leachate and electrolysis is performed by passing an alternating current, copper telluride is deposited on the bottom of the electrolytic cell. The reason for this is presumed as follows. That is, each electrode alternately becomes a cathode or an anode by an alternating current, and the elution of copper from the anode and the deposition of copper at the cathode are repeated. During this time, HTeO ₂ ⁺ in the liquid
Is reduced by metallic copper or copper ions on the electrode surface, forms Cu ₂ Te and precipitates on the electrode surface, and is immediately deposited on the electrode surface or the bottom of the electrolytic cell by the alternating current between the anode and the cathode. Conceivable.

As described above, in the present invention, electrolysis is performed using the copper electrode. As shown in the comparative example, when electrolysis is performed using a Pb anode which is an insoluble anode, the tellurium concentration in the electrolytic tail solution is 5.30.
It does not fall below g /, and the recovery rate of tellurium is poor.

Next, the present invention performs electrolysis using alternating current. When electrolysis is performed by a direct current, the anode becomes passivated and it becomes impossible to carry electricity. When an alternating current is used, the electrodes are alternately switched between the cathode and the anode, so there is no problem of passivation due to an increase in the concentration of kinetic ions in the liquid. As a result of preventing passivation, the cell voltage is 1/2 to 1/3 that of DC, and there is an advantage that the power consumption is remarkably small. With the precipitation of copper telluride,
The copper of the anode elutes in the liquid and the amount of the anode gradually decreases, but since the electrodes are alternately switched to the cathode and the anode, both electrodes are evenly reduced, and it is not necessary to replace the electrodes during the electrolysis work. In this respect, when direct current electrolysis is performed, the above-mentioned passivation is prevented and the electrolysis does not replace the anode and the cathode. It becomes necessary to replace the and the work becomes complicated.

The copper telluride deposited on the bottom of the tank is extracted, the tellurium is refined through a distillation process, and the residue containing copper as a main component is sent to copper smelting.

[Effects of the Invention] According to the present invention, tellurium can be easily recovered as copper telluride from a tellurium-containing solution such as a sulfuric acid leaching solution of copper electrolytic slime.

Since the present invention performs electrolysis using an alternating current, the electrodes are alternately switched between the cathode and the anode, and the surface of the electrodes is not passivated, and high tellurium recovery efficiency can be achieved.

In addition, the tellurium recovery efficiency is high, and the tellurium concentration in the liquid is 10%.
Since it can be reduced to 0 ppm or less, in copper electrolysis, after removing tellurium from the raw slime leaching solution by this method, the slime that has undergone decopperization electrolysis can be directly fed to the electrolysis step for repeated use. In this respect, conventionally, the effect of removing tellurium is low, and the content of other impurities is large, so that slime after decoppering electrolysis is sent back to the smelting step, resulting in poor utilization efficiency.

Furthermore, in the method of the present invention, since the electrodes are alternately switched to the cathode and the anode, the elution of copper in the electrodes is uniform, and since the weight loss of the electrodes progresses evenly, it is not necessary to replace the electrodes during electrolysis. Good efficiency.

In addition, since the electric power to the electrolysis plant is usually supplied by alternating current, there is no need to convert it to direct current and rectifying equipment is not required, and the equipment cost is about 1/10 of that when using direct current.

[Example] Example 1 The method of the present invention was carried out using a sulfuric acid leaching solution of raw slime in copper electrolysis. The results are shown in Table 1. The current density was 200 A / m ² , and the time required to reach a steady state after the start of electrolysis was 48 hours.

Example 2 The method of the present invention was carried out on the leachate having a higher free acid concentration (FA concentration) and a lower tellurium concentration than in Example 1. The results are shown in Table 2.

The current density was 200 A / m ² , and the time required to reach a steady state after the start of electrolysis was 36 hours.

Example 3 From Example 1, the method of the present invention was carried out using a leachate having a high acid and copper concentration and hydrochloric acid added. The result is the third
Shown in the table. The current density was 200 A / m ² , and the time required to reach a steady state after the start of electrolysis was 24 hours.

As shown in this example, the addition rate of hydrochloric acid improves the recovery rate of tellurium.

Example 4 The present invention was carried out by adding glucose as a reducing agent to the leachate of Example 1. The results are shown in Table 4.

The electrolytic density was 200 A / m ² , and the time required to reach a steady state was 48 hours. As is clear from the results of this example, the addition of a reducing agent such as glucose does not improve the tellurium recovery rate as in the case of adding hydrochloric acid as shown in Example 3.

Comparative Example 1 Table 5 shows the recovery rate of tellurium in decopperization electrolysis using a lead anode.

As shown in this comparative example, the concentration of tellurium in the tail solution was 5.30 g / l even when the copper concentration in the tail solution was electrolyzed to 0.17 g / l, and the tellurium removal recovery rate was poor.

Comparative Example 2 The leachate was continuously fed and electrolyzed under the same conditions as in Example 1 except that a direct current was used.

The results are shown in Table 6.

As shown in Table 6, the concentration of tellurium in the tail solution is 0.79 g / l when electrolysis is performed using a direct current, and the tellurium concentration is about 8 times that of the recovery method of the present invention. It remains without being recovered.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shosaku Hayashi 28 Minami Onamahamagawa-cho, Onahama, Iwaki, Fukushima Prefecture

Claims (2)

[Claims] 1. A method for recovering tellurium in which a tellurium-containing liquid is electrolyzed with an alternating current using a copper electrode to deposit copper telluride and recover as copper telluride. 2. A sulfuric acid leaching solution of raw slime produced by copper electrolytic refining is supplied to an electrolytic cell equipped with a copper electrode, and electrolysis is carried out by an alternating current to deposit and recover copper telluride. Tellurium recovery method described.