JP6933151B2 - How to recover selenium from copper electrolytic slime - Google Patents

Description

The present invention relates to a method for recovering a platinum group element, particularly high-purity selenium having low platinum grade, from copper electrolytic slime.

As for the treatment for recovering valuable gold from copper electrolytic slime, both the dry method and the wet method have been put into practical use. In particular, there are various wet methods, and one example thereof is the method described in Patent Document 1.

In the method disclosed in Patent Document 1, water is added to copper electrolytic slime to form a slurry, and chlorine gas is blown into the copper electrolytic slime 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 the organic phase, and then the extraction residue is brought into contact with trioctylmethylammonium chloride and tributyl phosphate to extract platinum group elements. .. Then, sulfur disulfide is blown into the extraction residual liquid, the redox potential (reference electrode: Ag / AgCl) is maintained at 400 mV to 500 mV to selectively reduce selenium, and then the redox potential is maintained at 290 mV to 380 mV. By doing so, tellurium is reduced and recovered.

Further, as another method for recovering platinum group elements from the extraction residual liquid from which gold has been separated as described above, Patent Document 2 describes platinum by contacting the extraction residual liquid from which gold has been separated with a polyamine type anion exchange resin. A method of adsorbing and separating group elements has been proposed. Selenium and tellurium remaining in the residual liquid after adsorbing platinum group elements with an anion exchange resin such as this polyamine type anion exchange resin are sulfur disulfide, as in the method disclosed in Patent Document 1 described above. It can be reduced and recovered by blowing in.

Further, as a method for removing platinum group elements remaining as impurities in the recovered selenium and tellurium, particularly palladium, Patent Document 3 describes sulfur disulfide in the residual liquid after adsorbing the platinum group elements with an anion exchange resin. Disclosed is a method of adding a reducing agent (adding a partial reduction step) before blowing in, and removing the platinum group elements that could not be completely removed by the anion exchange resin as a precipitate.

Specifically, a slurry of copper electrolytic slime is leached with chlorine, the leachate is brought into contact with an organic solvent to extract gold, and the extraction residual liquid is brought into contact with an anion exchange resin to adsorb platinum group elements. In the method of blowing sulfur dioxide into the residual liquid after adsorption to reduce and recover selenium, the chloride concentration in the residual liquid after adsorption is adjusted to the range of 2.0 mol / L to 2.5 mol / L, and then the adsorption thereof. While adjusting the temperature of the residual liquid in the range of 30 ° C to 50 ° C, sodium hydrogen sulfite, which is a solution having a concentration of 35% by weight to 36% by weight in terms of _{NaHSO 3 as the residual liquid after adsorption, is added to the residual liquid after adsorption.} The method is characterized in that 1% by volume to 3% by volume is added to the amount, and the produced precipitate mainly containing palladium is filtered and separated, and then sulfur dioxide is blown into the obtained filtrate.

Such a method disclosed in Patent Document 3 is a useful method capable of recovering selenium having a low palladium grade by improving the conventional method. However, there is no description about a method for effectively separating and recovering platinum (Pt) among the platinum group elements to recover high-purity selenium having a low platinum grade. Since the copper electrolytic slime contains platinum in a predetermined ratio and is a valuable metal, a method for effectively separating and recovering platinum from the copper electrolytic slime and recovering high-purity selenium. Is required.

Japanese Unexamined Patent Publication No. 2001-207223 Japanese Unexamined Patent Publication No. 2004-131745 Japanese Unexamined Patent Publication No. 2012-126611

The present invention has been proposed in view of such circumstances, and when recovering a valuable metal from a leachate obtained by leaching copper electrolytic slime with chlorine, the extraction residual liquid after gold is extracted and separated is an anion exchange resin. It is an object of the present invention to provide a method for recovering high-purity selenium having a low platinum grade from the residual liquid after adsorption.

The present inventor has made extensive studies to solve the above-mentioned problems. As a result, when the reduction behavior of platinum (Pt) and selenium among the platinum group elements was studied, ascorbic acid was added to the residual liquid after adsorption after contacting with an anion exchange resin to adsorb the platinum group elements. It has been found that platinum remaining in the residual liquid after adsorption can be preferentially reduced over selenium to form a precipitate and separated by adding the above, and the present invention has been completed.

(1) In the first invention of the present invention, a slurry of copper electrolytic slime is leached with chlorine, the leachate is brought into contact with an organic solvent to extract gold, and the extraction residual liquid is brought into contact with an anion exchange resin to form a platinum group. In the method of adsorbing an element and then blowing sulfur dioxide into the residual liquid after adsorption to reduce and recover selenium, ascorbic acid is added before blowing sulfur dioxide into the residual liquid after adsorption, and the produced platinum is contained. This is a method for recovering selenium from a copper electrolytic slime, in which selenium is recovered by blowing sulfur dioxide into the obtained filtrate after filtering and separating the precipitate.

(2) In the second invention of the present invention, in the first invention, the amount of ascorbic acid added is 10 to 100 times the molar amount of palladium and platinum (Pd + Pt) in the residual liquid after adsorption. This is a method for recovering selenium from copper electrolytic slime.

According to the present invention, platinum can be effectively recovered from the residual liquid after adsorption by reducing platinum, and high-purity selenium having a low platinum grade can be recovered.

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

The method for recovering selenium according to the present embodiment is a method for recovering selenium from copper electrolytic slime. Specifically, a slurry of copper electrolytic slime is leached with chlorine, and an organic solvent is brought into contact with the leachate to bring gold. Is extracted, the extraction residual liquid is brought into contact with an anion exchange resin to adsorb platinum group elements, and then sulfur dioxide is blown into the residual liquid after adsorption to reduce and recover selenium.

Then, in this method for recovering selenium, ascorbic acid is added after adsorption before blowing sulfur dioxide into the residual liquid, and the precipitate containing the produced platinum is filtered and separated, and then sulfur dioxide is added to the obtained filtrate. It is characterized by recovering selenium by blowing it. Here, platinum group elements such as platinum and palladium remain in the residual liquid after adsorption, although it depends on the adsorption force (adsorption rate) of the anion exchange resin.

In this method, by adding ascorbic acid to the residual liquid after adsorption, platinum (Pt), which is a platinum group element remaining in the residual liquid after adsorption, is preferentially reduced over selenium, and mainly platinum is reduced. The containing precipitate can be produced, and the produced precipitate can be effectively separated and removed by filtering. Then, by blowing sulfur dioxide into the filtrate obtained by filtration to reduce selenium, high-purity selenium having a low platinum grade can be precipitated and recovered. On the other hand, platinum, which is a valuable metal that has been reduced and precipitated, can also be effectively and efficiently recovered.

The organic solvent used for gold extraction and the anion exchange resin used for adsorbing platinum group elements may be those conventionally used. For example, bis (2-butoxyethyl) ether is preferable as the organic solvent used for gold extraction, and polyamine type anion exchange resin is preferably used as the anion exchange resin used for adsorption of platinum group elements. ..

As described above, in the step of reducing and recovering the platinum remaining in the adsorption residual liquid (hereinafter, also referred to as “platinum reduction separation step”), ascorbic acid (NaC ₆ H ₇ O ₆ ; L- (Also called sodium ascorbic acid) is used. Here, since the amount of platinum group elements contained in the residual liquid after adsorption after the adsorption treatment with the anion exchange resin is very small, for example, a reducing agent such as sulfur dioxide gas while monitoring only the oxidation-reduction potential of the liquid. It is not easy to control the amount of addition accurately. On the other hand, according to the method of adding ascorbic acid using a solution, the addition time, that is, the amount of addition can be controlled by a method such as using a metering pump, and the redox potential can also be controlled. It will be easy. Thereby, the reduction of platinum group elements such as platinum contained in a trace amount can be easily and accurately controlled.

The amount of ascorbic acid added is the molar amount of palladium and platinum (Pd + Pt) in the residual liquid after adsorption with an anion exchange resin as a solution having a concentration of 33% by weight to 38% by weight in terms of _{NaC 6} H ₇ O _{6 (total).} The amount is preferably 10 to 100 times the molar amount).

The larger the amount of ascorbic acid added, the more the amount of platinum reduced can be increased. However, since ascorbic acid is expensive, it is possible to set an upper limit commensurate with the amount of platinum recovered, including the cost of adding an addition device. preferable. In addition, if the amount of ascorbic acid added is too large, selenium is also involved in the precipitate produced by reduction and precipitates, so that it may not be possible to increase the amount of selenium recovered after separating from platinum. .. On the other hand, if the amount of ascorbic acid added is small, the amount of platinum contained in the residual liquid after adsorption may decrease, and the amount of platinum distributed to selenium when recovering selenium in the next step (in selenium). Platinum grade) may increase. Based on these facts, by setting the amount of ascorbic acid added to 10 to 100 times the molar amount of (Pd + Pt), platinum can be separated and recovered more effectively, and the platinum quality in selenium can be further reduced. , High quality selenium can be recovered.

Here, when ascorbic acid is added to the residual liquid after adsorption, the acid concentration (chloride ion concentration) is in the range of 1.7 mol / L to 2.3 mol / L prior to the addition of the reducing agent. It is preferable to do so.

In general, platinum ion chloride solution is present in the form represented by PtCl ₆ ^2-but this form hardly reduced increases the stability of chloride complexes with the chloride ion concentration increases, the selenium The selectivity is reduced and it becomes difficult to separate platinum.

For this reason, it is preferable to adjust the acid concentration in the residual liquid after adsorption prior to adding ascorbic acid. Specifically, the pH of the residual liquid after adsorption is adjusted to adjust the acid. The concentration is in the range of 1.7 mol / L to 2.3 mol / L. As described above, preferably, by adjusting the acid concentration in the range of 1.7 mol / L to 2.3 mol / L, the selectivity with selenium can be ensured, and platinum can be selectively reduced and precipitated. It will be easier.

The lower the acid concentration of the residual liquid after adsorption, the better the selectivity with selenium, but if the acid concentration is less than 1.7 mol / L, the amount of pH adjuster used to adjust the concentration will increase. In order to suppress the rise in liquid temperature due to the heat of neutralization, it is necessary to add cooling water or the like, which is inefficient.

As a method for adjusting the acid concentration, for example, when the acid concentration in the residual liquid after adsorption before adding the reducing agent is lower than the above range, chloride ions are formed in the form of sodium chloride, potassium chloride, hydrochloric acid or the like. Can be adjusted by replenishing the mixture or by heating and concentrating the residual liquid after adsorption. On the other hand, when the acid concentration is higher than the above range, water may be added to the residual liquid after adsorption to dilute it.

Further, the temperature of the residual liquid after adsorption when ascorbic acid is added to the residual liquid after adsorption and reduced is preferably adjusted to the range of 30 ° C. to 50 ° C. This temperature is the same when platinum is separated and recovered from the residual liquid after adsorption, and then sulfur dioxide is blown into the obtained filtrate to reduce and recover selenium. Even if the temperature of the residual liquid after adsorption is less than 30 ° C., platinum can be selectively reduced, but the reduction rate of platinum becomes slow. Therefore, when it is carried out on an industrial scale, there are disadvantages such as a slow reduction rate and a reaction tank having a scale commensurate with the required processing amount, in addition to the labor and time required for the operation.

On the other hand, if the temperature of the residual liquid after adsorption exceeds 50 ° C., the selenium produced becomes difficult to handle, which is not preferable. That is, the form of selenium changes to amorphous red selenium when the reduction temperature is 50 ° C. or lower, glassy amorphous selenium when the reduction temperature exceeds 50 ° C. and up to about 60 ° C., and crystalline selenium when the reduction temperature is 70 ° C. or higher. It is desirable to avoid the formation of glass-like amorphous selenium because it forms dumplings and easily adheres to the inside of the reaction vessel and the stirring blade. Further, when the temperature is higher than 50 ° C., the platinum is redissolved, so that the reduction of platinum is difficult to proceed. For these reasons, it is preferable that the reaction temperature is up to 50 ° C.

The filtrate after the precipitate containing platinum is filtered and separated from the residual liquid after adsorption by the platinum reduction separation step can be recovered by sequentially reducing selenium and tellurium by the same treatment as before. That is, in the selenium reduction step, selenium is selectively reduced by blowing sulfur disulfide to maintain the oxidation-reduction potential (reference electrode: Ag / AgCl) at 400 mV to 500 mV. Further, in the next reduction step of tellurium, tellurium is reduced and recovered by maintaining the redox potential at 290 mV to 380 mV. As the reducing agent used for reducing selenium and tellurium, sulfur dioxide gas, which is inexpensive and easy to handle, is preferable.

By the way, in the method disclosed in Patent Document 3 proposed by the applicant, sodium hydrogen sulfite, which is a reducing agent, is added to the residual liquid after adsorption, thereby reducing the palladium remaining in the residual liquid after adsorption and being effective. It is separated and removed. However, Patent Document 3 does not show the separation and removal of platinum among the platinum group elements. When a platinum group element is adsorbed on the extraction residual liquid after gold is separated using an anion exchange resin, it is conceivable that the adsorption rate of platinum due to the anion exchange resin may decrease. Moreover, as shown in Examples described later, ascorbic acid added to the residual liquid after adsorption by the method according to the present embodiment more effectively reduces platinum than palladium contained in the residual liquid after adsorption. be able to. In other words, when only sodium bisulfite disclosed in Patent Document 3 is added, it is unclear whether platinum remaining in the residual liquid after adsorption can be effectively separated and removed.

Hereinafter, examples of the present invention will be described in more detail, but the present invention is not limited to the following examples.

(About residual liquid after adsorption)
Water was added to the copper electrolytic slime produced by copper electrorefining to adjust the slurry concentration to 200 g / L. This slurry was leached by blowing chlorine gas from a cylinder to obtain a leaching solution having the composition shown in Table 1 below. Then, 1.5 liters of bis (2-butoxyethyl) ether as an organic extractant is mixed with 1.5 liters of the obtained leachate, shaken for 5 minutes, and then allowed to stand to contain gold contained in the leachate. Was extracted into the organic phase and separated.

Subsequently, the extraction residual liquid after separating the gold was placed in a glass column filled with 100 ml of a polyamine type anion exchange resin (manufactured by Purolite, trade name: A830W type) at a flow rate of SV = 2 (200 ml / hr). , The liquid was passed under the condition that the liquid volume was BV = 15 (1500 ml), and the platinum group element contained in the extraction residual liquid was adsorbed. The residual liquid after adsorption after passing through the resin was collected and analyzed using an ICP analyzer (however, Cu, As, Sb, and Bi were excluded). Table 1 below shows the composition of the obtained residual liquid after adsorption.

The acid concentration (chloride ion concentration) of the residual liquid after adsorption was 2.5 mol / L.

(About the type of reducing agent)
The reducing agents used in the following examples and the like are as follows.
Reducing agent 1: Sodium ascorbate (concentration 35 wt% solution)

[Example 1]
Put 1.5 liters of residual liquid after adsorption in a heat-resistant glass beaker with a capacity of 3 liters, heat it to adjust the temperature to 50 ° C, and stir with a _{three-one motor to make an ascorbic acid solution (NaH 2} (C 3 H _5). A concentration of 35% by weight in terms of O (COO) ₃ ) was added. The amount of addition is ideal for the total number of moles (Pt + Pd) of platinum (Pt) and palladium (Pd) contained in the residual liquid after adsorption. The required amount was set to 1 equal amount, 10 equal amounts (10 times amount), 30 equal amounts (30 times amount), and 100 equal amounts (100 times amount).

After adding ascorbic acid at each addition amount (after the platinum reduction separation step), the concentrations of platinum and palladium contained in the filtrate (post-reduction liquid) obtained by solid-liquid separation are analyzed using an ICP analyzer. bottom. Table 2 below shows the concentration ratios (ppm) of platinum and palladium to the concentration of selenium contained in the filtrate, and regarded them as platinum grade and palladium grade in selenium recovered by reduction.

As shown in Table 2, platinum (Pt) in selenium could be effectively reduced by adding ascorbic acid and reducing it. In particular, by adding an ascorbic acid solution in an amount of 30 times the molar amount of (Pt + Pd) in the residual liquid after adsorption and reducing the amount, the amount is reduced to 1/10 or less as compared with the case of no treatment. I was able to.

Moreover, from the results of platinum and palladium shown in Table 2, by adding ascorbic acid to the residual liquid after adsorption, the effect on platinum is higher than that of palladium contained in the residual liquid after adsorption, and separation is more selective. It turned out that it could be removed.

From the above results, when platinum group elements are adsorbed on the extraction residual liquid after gold separation using an anion exchange resin, the adsorption rate of platinum by the anion exchange resin is particularly reduced. Even if there was, it was found that by adding ascorbic acid to the residual liquid after adsorption, the platinum can be effectively reduced and separated and removed, and high-purity selenium with low platinum grade can be recovered. It was also found that platinum can be separated and removed more effectively by setting the amount of ascorbic acid added within a specific range.

Claims (2)

The slurry of copper electrolytic slime is leached with chlorine, and the leachate is brought into contact with an organic solvent to extract gold. In the method of blowing sulfur dioxide to reduce and recover selenium,
Ascorbic acid was added to the residual liquid after adsorption before blowing sulfur dioxide into the residual liquid.
A method for recovering selenium from copper electrolytic slime, in which the produced precipitate containing platinum is filtered and separated, and then sulfur dioxide is blown into the obtained filtrate to recover selenium. The method for recovering selenium from copper electrolytic slime according to claim 1, wherein the amount of ascorbic acid added is 10 to 100 times the molar amount of palladium and platinum (Pd + Pt) in the residual liquid after adsorption.