JP5454461B2 - Method for recovering selenium from copper electrolytic slime - Google Patents

Description

  The present invention relates to the recovery of platinum group elements from copper electrolytic slime, and more particularly to a method for recovering high-purity selenium with low palladium quality.

  As for the process of recovering valuable metal from copper electrolytic slime, both the dry method and the wet method have been put into practical use. There are various wet methods in particular, and one example is the method described in Japanese Patent Application Laid-Open No. 2001-207223 (Patent Document 1).

  In this method, water is added to copper electrolytic slime to form a slurry, and chlorine gas is blown to leach valuable metals such as gold, platinum group elements, selenium and tellurium. The obtained leachate is brought into contact with bis (2-butoxyethyl) ether to extract and separate gold into an organic phase, and then the extraction residue is brought into contact with trioctylmethylammonium chloride and tributyl phosphate to extract platinum group elements. . Sulfur disulfide is blown into this extraction residual liquid, the redox potential (reference electrode: Ag / AgCl) is maintained at 400 to 500 mV to selectively reduce selenium, and then the redox potential is maintained at 290 to 380 mV. To reduce and recover tellurium.

  As another method for recovering a platinum group element from an extraction residual liquid from which gold has been separated as described above, JP 2004-131745 A (Patent Document 2) discloses an extraction residual liquid from which gold has been separated as a polyamine type anion. A method of adsorbing and separating platinum group elements by contacting with an exchange resin has been proposed. Selenium and tellurium remaining in the residual liquid after the platinum group element is adsorbed by an anion exchange resin such as this polyamine type anion exchange resin can be obtained by blowing sulfur disulfide in the same manner as in the method described in Patent Document 1. What is necessary is just to reduce | restore and collect | recover.

  However, the copper electrolytic slime contains various elements such as Ba, Pb, Bi, Fe, Cu, As, Se, Sn, Sb, Te, Au, Ag, and platinum group elements. When copper electrolytic slime containing these elements is leached with chlorine gas, various elements such as Cu, Se, As, Te, Sb, Bi, in addition to valuable elements such as gold and platinum group elements, which are the purpose of recovery Are leached at the same time, so these elements must be treated as impurities.

  On the other hand, impurities in copper smelting vary depending on the quality of the ore used as a raw material. In recent years, arsenic (As) quality has risen remarkably, and the amount of As contained in the copper electrolytic slime is also increasing. However, since it is not easy to separate arsenic contained in the raw material ore, the As concentration in the leachate obtained by leaching copper electrolytic slime with chlorine gas tends to increase.

  For such a leachate with a high As concentration, after extracting and separating gold as described above, the platinum group element is adsorbed and separated from the extraction residual liquid with an anion exchange resin such as a polyamine type anion exchange resin. There is a problem that palladium (Pd) that is adsorbed and removed is reduced. That is, it was found that when the As concentration in the leachate exceeds approximately 5.5 g / l, the adsorption rate of Pd is reduced due to As being disturbed. As a result, it was inevitable that the quality of Pd in Se recovered from the residual liquid after adsorption increased and the quality of selenium deteriorated.

JP 2001-207223 A JP 2004-131745 A

  In the present invention, in view of the above-described conventional circumstances, when recovering a valuable metal from a leachate obtained by leaching a copper electrolytic slime having a high arsenic concentration, the extraction residual solution after extracting and separating gold is treated with an anion exchange resin. Then, it aims at providing the method of collect | recovering highly purified selenium from the residual liquid after the adsorption | suction.

  In order to achieve the above object, the present inventors have conducted intensive research on the reduction behavior of selenium and platinum group elements, particularly selenium and palladium, in the leaching solution obtained by leaching copper electrolysis slime. After adsorbing and separating group elements, it was found that by adding sodium hydrogen sulfite as a reducing agent to the residual liquid after the adsorption, it was possible to reduce and preferentially precipitate palladium over selenium. Has been completed.

  That is, the method for recovering selenium from copper electrolytic slime provided by the present invention is a method in which a slurry of copper electrolytic slime is leached with chlorine, an organic solvent is brought into contact with the leached liquid to extract gold, and the extraction residual liquid is subjected to anion exchange. After adsorption of platinum group element by contacting with resin, in the method to recover selenium by blowing sulfur dioxide into the residual liquid after adsorption, sodium hydrogen sulfite is added before sulfur dioxide is blown into the residual liquid after adsorption Then, after the precipitate mainly containing palladium is filtered and separated, sulfur dioxide is blown into the obtained filtrate.

  In the method for recovering selenium from the copper electrolytic slime according to the present invention, the chloride concentration in the residual liquid after adsorption is adjusted to the range of 2.0 to 2.5 mol / l before adding sodium hydrogen sulfite. It is preferable. Moreover, when adding sodium hydrogen sulfite, it is preferable to adjust the temperature of the residual liquid after adsorption to the range of 30-50 degreeC.

Furthermore, in the method for recovering selenium from the copper electrolytic slime according to the present invention, the amount of sodium hydrogen sulfite added is 1 to 1 with respect to the amount of residual liquid after adsorption as a solution having a concentration of 35 to 36% by weight in terms of NaHSO ₃ . It is preferably 3% by volume. Further, the amount of sodium bisulfite added can be controlled by the oxidation-reduction potential. In this case, sodium bisulfite may be added so that the oxidation-reduction potential of the residual liquid after adsorption is in the range of 1050 to 800 mV. preferable.

  According to the present invention, even in the leachate obtained by leaching chlorine electrolytic copper slime with high arsenic quality in recent years, palladium is reduced and recovered following the extraction separation of gold and the adsorption separation of the platinum group element, and the palladium Low quality and high purity selenium can be recovered. As a result, recovery loss can also be reduced for platinum group elements, particularly palladium.

It is a graph which shows the relationship between the oxidation-reduction potential of the residual liquid after adsorption | suction at the time of adding sodium hydrogensulfite in Example 1, and the density | concentration of selenium, and palladium. It is a graph which shows the relationship between the chloride density | concentration in the residual liquid after adsorption | suction at the time of adding sodium hydrogen sulfite in Example 3, and palladium concentration.

  In the present invention, when recovering valuable metals, particularly selenium, from a leachate obtained by leaching a copper electrolysis slime slurry with chlorine, an extraction residual solution obtained by extracting gold with an organic solvent is brought into contact with an anion exchange resin to remove a platinum group element. After the adsorption, palladium remaining in the residual liquid after adsorption is reduced with sodium bisulfite, and the precipitate mainly containing palladium is separated by filtration. Next, sulfur dioxide is blown into the obtained filtrate to reduce selenium, thereby precipitating and collecting high-purity selenium having a low palladium quality.

  In addition, the organic solvent used for the said gold extraction, and the anion exchange resin used for adsorption | suction of a platinum group element may be used conventionally. For example, bis (2-butoxyethyl) ether is preferred as the organic solvent used for gold extraction, and polyamine type anion exchange resin is preferably used as the anion exchange resin used for the adsorption of platinum group elements.

In the above reduction and separation step of palladium, sodium bisulfite (NaHSO ₃ ; also referred to as sodium bisulfite) is used as a reducing agent. The amount of platinum group elements such as palladium contained in the residual liquid after adsorption with an anion exchange resin is very small, so the amount of reducing agent such as sulfur dioxide gas can be accurately controlled while monitoring only the redox potential of the liquid. It is not easy. In contrast, when sodium bisulfite is used in a solution, the addition time, that is, the addition amount can be controlled by a method such as using a metering pump, and the oxidation-reduction potential can be easily controlled. There is an advantage that the reduction of a platinum group element such as palladium can be easily and accurately controlled.

As the amount of sodium hydrogen sulfite added is increased, the reduction amount of palladium can be increased, but at the same time, the coprecipitation amount of selenium is increased, so that a recovery loss is likely to occur. Conversely, if the amount of sodium bisulfite added is small, the amount of palladium reduced will decrease, and the amount of palladium distributed to selenium will increase when selenium is recovered in the next step, resulting in poor quality of selenium. To avoid these disadvantages, the addition amount of sodium bisulfite is, NaHSO ₃ as a solution concentration of 35 to 36 wt% in terms of 1-3 vol% with respect to the liquid amount of the post-adsorption residual liquid in the anion exchange resin It is preferable to add.

  The amount of sodium hydrogen sulfite added can also be controlled by the redox potential (reference electrode: Ag / AgCl). This is because the addition of sodium bisulfite, which is a reducing agent, reduces palladium in preference to selenium in the initial stage of reduction. Specifically, palladium is selectively reduced over selenium by adding sodium bisulfite so that the redox potential of the residual liquid after adsorption is in the range of 1050 to 800 mV. Only the precipitate made of palladium can be separated.

In the reduction and separation step of palladium by adding sodium hydrogen sulfite, the chloride ion concentration in the residual liquid after adsorption should be adjusted to the range of 2.0 to 2.5 mol / l before adding sodium hydrogen sulfite. Is preferred. In general, palladium ions in a chloride solution exist in a form represented by PdCl ₆ ^2- . In this form, when the chloride ion concentration increases, the stability of the chloride complex increases and it is difficult to reduce the selenium. And the selectivity is reduced, making separation difficult. Therefore, by adjusting the chloride ion concentration in the residual liquid after adsorption to 2.5 mol / l or less, selectivity with selenium is ensured, and it becomes easy to selectively reduce and precipitate palladium.

  On the other hand, the lower the chloride ion concentration, the better the selectivity with selenium. However, when the chloride ion concentration is less than 2.0 mol / l, impurities such as antimony and bismuth are used when reducing and separating selenium in the next step. Since it is also hydrolyzed and easily precipitated, the quality of the recovered selenium may be lowered. For these reasons, it is preferable to adjust and manage the chloride ion concentration in the residual liquid after adsorption within the range of 2.0 to 2.5 mol / l.

  In the above reduction and separation step of palladium, if the chloride ion concentration in the residual liquid after adsorption before adding sodium bisulfite is lower than the above basic range, it is in the form of sodium chloride, potassium chloride, hydrochloric acid, etc. The chloride ion concentration can be adjusted by replenishing chloride ions or by heating and concentrating the residual liquid after adsorption. On the other hand, when the chloride ion concentration is high, water may be added to the residual liquid after adsorption to dilute.

  Moreover, it is desirable to adjust the temperature of the post-adsorption residual liquid at the time of reduction in the range of 30-50 degreeC. Even if the temperature of the residual liquid after adsorption is less than 30 ° C., selenium and palladium can be selectively reduced, but the reduction rate of palladium becomes slow. Therefore, when it implements on an industrial scale, operation takes time and effort, and there are disadvantages such as a slow reduction rate and a reaction tank of a scale corresponding to the required throughput.

  On the other hand, if the temperature of the residual liquid after adsorption exceeds 50 ° C., the generated selenium is difficult to handle, which is not preferable. That is, the form of selenium changes to amorphous red selenium at a reduction temperature of 50 ° C. or lower, glassy amorphous selenium at 50 to 60 ° C., and crystalline selenium at 70 ° C. or higher. Since glassy amorphous selenium tends to adhere to the inside of the reaction vessel and the stirring blade in the form of a dumpling, it is desirable to avoid the generation. Further, when the temperature is higher than 50 ° C., palladium is redissolved, so that the reduction of palladium is difficult to proceed. For these reasons, the reaction temperature is preferably 50 ° C.

The filtrate after separating palladium by filtration from the residual liquid after adsorption in the palladium reduction and separation step can be recovered by sequentially reducing selenium and tellurium by the same treatment as before. That is, in the selenium reduction step, sulfur dioxide is blown in to maintain the redox potential (reference electrode: Ag / AgCl) at 400 to 500 mV, thereby selectively reducing selenium. In the next tellurium reduction step, the redox potential is reduced. Is maintained at 290-380 mV to reduce and recover tellurium. As a reducing agent used for reduction of selenium and tellurium, sulfur dioxide gas which is inexpensive and easy to handle is preferable.

[Example 1]
Water was added to the copper electrolytic slime produced by the copper electrolytic purification, and the slurry concentration was adjusted to 200 g / l. Chlorine gas was blown into the slurry from a cylinder to obtain a leachate having the composition shown in Table 1 below. To 1.5 liters of the leachate, 1.5 liters of bis (2-butoxyethyl) ether as an organic extractant is mixed, shaken for 5 minutes, and allowed to stand to allow the gold contained in the leachate to enter the organic phase. Extracted and separated.

  Next, the extraction residual liquid after separating the gold was applied to a glass column packed with 100 ml of a polyamine type anion exchange resin (product name: A830W type, manufactured by Purolite), and the flow rate was SV = 2 (200 ml / hr). The liquid was passed under the condition that the amount was BV = 15 (1500 ml), and the platinum group element contained in the extraction residual liquid was adsorbed. The post-adsorption residual liquid after passing through the resin was put together and analyzed using an ICP analyzer (however, Cu, As, Sb, and Bi were excluded). The composition of the obtained residual liquid after adsorption is shown in Table 1 below together with the composition of the leachate.

Next, the reduction behavior of selenium and palladium was investigated for the residual liquid after adsorption after passing through the ion exchange resin. That is, 1.5 liters of the remaining liquid after adsorption is put in a heat-resistant glass beaker having a capacity of 3 liters, heated to adjust the temperature to 50 ° C., and stirred with a _three-one motor, with a sodium bisulfite solution (in terms of NaHSO ₃₎ . Concentrations of 35 to 36% by weight) were added sequentially. At that time, sampling was performed every 10 minutes to analyze the concentrations of selenium and palladium remaining in the liquid, and the oxidation-reduction potential (reference electrode: Ag / AgCl) of the liquid was measured. The obtained results are shown in FIG.

  From the results of FIG. 1, it can be seen that palladium can be reduced and separated in preference to selenium in the initial stage of reduction. Specifically, by controlling the oxidation-reduction potential in the range of 1050 to 800 mV while adding a sodium bisulfite solution, palladium is selectively reduced, and a precipitate mainly composed of palladium rather than selenium can be obtained. . The chloride concentration in the residual liquid after adsorption was 2.3 mol / l as measured by a titration method.

[Example 2]
About 2 liters of the solution after adsorption of the platinum group with the ion exchange resin in Example 1 above, that is, about 2 liters of the residual liquid after adsorption having the composition shown in Table 1 above, is divided into 9 equal portions of 200 ml, and each volume is 0. Place in a .5 liter heat-resistant glass beaker.

  About each said post-adsorption residual liquid, each liquid temperature is maintained at each temperature of 20 degreeC to 80 degreeC shown in following Table 2, and it stirs with a slur one motor, a sodium bisulfite solution (concentration 35-36 weight%) Was added in the range of 1 to 4% by volume (2 to 8 ml) with respect to each liquid amount and stirred for 1 hour.

  After a predetermined time, the selenium and palladium concentrations of the filtrate obtained by solid-liquid separation were analyzed by ICP, and the selenium and palladium concentrations in the obtained filtrate are shown in Table 2 below. Moreover, the external appearance of the collect | recovered deposit was observed visually, and the result was combined with following Table 2, and was shown.

  As shown in Table 2 above, when the liquid temperature is 20 ° C., the reduction reaction is slow, so even if 1 to 2% by volume of sodium bisulfite solution is added, no significant reduction occurs with stirring for 1 hour. Addition up to volume percent was required. In addition, when the liquid temperature is 60 ° C. or higher, a massive reduced product or a coarse black powder having a massive collapse is obtained, and these precipitates are not preferable in view of industrial handling.

[Example 3]
In Example 1 above, a solution after the platinum group was adsorbed with an ion exchange resin, that is, a residual solution after adsorption, was prepared, divided into 100 ml portions, and the liquid temperature was maintained within the range of 40 to 43 ° C. After the adsorption, hydrochloric acid was added to the residual liquid to adjust the chloride concentration. Then, in the same manner as in Example 1, the sodium bisulfite solution was added in an amount of 1.5 to 2.0% by volume (1.5%). ~ 2 ml) was added. Thereafter, the precipitate was filtered and separated, and the chloride concentration and palladium concentration of the filtrate after the reduction were analyzed, and the obtained results are shown in FIG.

As shown in FIG. 2, it can be seen that the smaller the chloride concentration, the easier the palladium is reduced and removed. That is, in order to reliably obtain high-purity selenium with low palladium quality by the subsequent blowing of sulfur dioxide , the chloride concentration of the residual liquid after adsorption is set to 2.0 to 2.5 mol before adding sodium bisulfite. It is preferable to adjust to the range of / l.

[Example 4]
In Example 1 above, a solution after the platinum group was adsorbed with an ion exchange resin, that is, a post-adsorption residual solution, was prepared, divided into three equal portions of 1.5 liters, and each glass beaker with an overflow tube ( 1 liter). The temperature is maintained at 45 to 50 ° C. while stirring with a _three-one motor, and then a sodium bisulfite solution (concentration of 35 to 36% by weight in terms of NaHSO ₃ ) is adsorbed with respect to the amount of residual liquid after adsorption. 1, 2, 3 volume% was added.

  After adding a sodium hydrogen sulfite solution and reacting for 30 minutes, the produced precipitate was separated by filtration, and the palladium concentration and selenium concentration in the filtrate were analyzed. Further, in order to confirm the quality of the collected selenium, sulfur dioxide was blown into the filtrate obtained by filtration until the oxidation-reduction potential reached 500 mV (reference electrode: Ag / AgCl), and selenium was precipitated and collected. The collected selenium precipitate was dried and analyzed for palladium quality.

  Table 3 below shows the concentration of selenium and palladium in the residual liquid after adsorption and the filtrate after reduction of paradium, and the palladium quality of the selenium powder recovered as a precipitate for each amount of sodium bisulfite solution added. From this result, it can be seen that the palladium quality of the recovered selenium powder decreases as the amount of sodium bisulfite added increases in the range of 1 to 3% by volume.

  If the amount of sodium bisulfite added is less than 1% by volume, the palladium quality in selenium becomes too high, which is not preferable from the viewpoint of maintaining the quality of selenium. On the other hand, when the addition amount of sodium hydrogen sulfite exceeds 3% by volume, the reduction amount of selenium together with palladium increases, and the recovery loss of selenium increases. In addition, the amount of sodium hydrogen sulfite, which is a reducing agent, is increased, resulting in an increase in cost.

[Comparative Example 1]
In Example 1 above, a solution after the platinum group is adsorbed with an ion exchange resin, that is, a residual liquid after adsorption, is prepared, and 1.5 liters of the residual liquid after adsorption is put in a heat-resistant glass beaker having a capacity of 3 liters. While maintaining at 80 ° C. and stirring with a three-one motor, a sodium bisulfite solution (concentration of 35 to 36% by weight) was added until the oxidation-reduction potential (reference electrode: Ag / AgCl) was reduced to 500 mV.

  Then, it filtered and solid-liquid separated, Sulfur dioxide gas was blown into the obtained filtrate, and selenium was deposited. After the collected selenium powder was dried and analyzed for palladium quality, the palladium quality in the selenium powder was 1300 ppm, and the quality was significantly reduced compared to Example 4 above.

Claims (2)

The copper electrolysis slime slurry is leached with chlorine, and the leachate is contacted with an organic solvent to extract gold. The extracted residue is brought into contact with an anion exchange resin to adsorb platinum group elements, and then the residual solution after adsorption. In the method in which sulfur dioxide is blown into the selenium to reduce and recover selenium, the chloride concentration in the post-adsorption residual liquid is adjusted to a range of 2.0 to 2.5 mol / l, and then the post-adsorption residual liquid While adjusting the temperature in the range of 30 to 50 ° C., 1 to 3 volumes of sodium bisulfite in a concentration of 35 to 36% by weight in terms of NaHSO ₃ was added to the residual liquid after adsorption with respect to the liquid volume of the residual liquid after adsorption. A method for recovering selenium from copper electrolytic slime, wherein the precipitate containing mainly palladium is added by filtration and separated by filtration, and then sulfur dioxide is blown into the obtained filtrate. The method for recovering selenium from copper electrolytic slime according to claim 1, wherein sodium bisulfite is added so that the redox potential of the residual liquid after adsorption is in the range of 1050 to 800 mV .

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