JP6835577B2 - How to collect valuables - Google Patents

Description

The present invention relates to a method for recovering valuable resources.

In the copper pyrometallurgy, copper concentrate is melted to obtain 99% or more blister copper in a converter and a refining furnace, and then electrolytic copper having a purity of 99.99% or more is produced in the electrolytic refining process. In recent years, metal scraps containing precious metals derived from electronic parts have been introduced as recycling raw materials in converters, and valuable resources other than copper are precipitated as slime during electrolytic refining.

In addition to gold, silver, platinum and palladium, rare metals such as ruthenium, rhodium and iridium, and selenium and tellurium contained in copper concentrate are also concentrated in this slime. These elements are separated and recovered individually as copper smelting by-products.

A hydrometallurgy method is often applied to the treatment of this slime. For example, Patent Document 1 discloses a method in which silver is recovered from slime with hydrochloric acid-hydrogen peroxide, the dissolved gold is recovered by solvent extraction, and then other valuable resources are sequentially reduced and recovered with sulfur dioxide. Patent Document 2 discloses a method of recovering gold and silver by the same method, reducing valuable resources with sulfur dioxide to precipitate them, and distilling and removing only selenium to concentrate precious metals.

The solution after recovering the noble metal contains rare metal ions, tellurium, and selenium, and it is necessary to recover these valuable resources. As a recovery method, a method of recovering the precipitate generated by the reducing agent and a method of mixing the solution with copper concentrate, drying it with a dryer, and repeating it in a smelting furnace are known.

In particular, as shown in Patent Document 1, the method of recovering the precipitate generated by sulfur dioxide has many advantages in terms of cost and production scale. In addition, since each element is sequentially precipitated, it is also effective for separation and purification.

Japanese Unexamined Patent Publication No. 2001-316735 Japanese Unexamined Patent Publication No. 2004-190134

In the method of recovering valuable resources using sulfur dioxide, the valuable resources are sequentially reduced and recovered after dissolution, but there are not a few valuable resources that finally remain in the liquid. However, if heating and sulfur dioxide supply are continued for a long time, all valuable resources can be recovered, but there are problems of production efficiency and energy cost per unit time.

If a stronger reducing agent such as hydrazine or zinc powder is added, most of the valuable resources can be recovered, but there are problems such as reagent cost and generation of various gases. In addition, the cost required for wastewater treatment will increase.

In particular, it is preferable to recover almost all of selenium, tellurium, and ruthenium at the final stage. Ruthenium is emitted at a relatively high concentration regardless of the platinum group element. Emission standards have been set for selenium and tellurium, and it is necessary to ensure that they are collected. In the wastewater treatment process, it is often treated by the coprecipitation method, and the valuable resources recovered by coprecipitation are sludge containing a coprecipitation agent and are treated as industrial waste. It is not preferable because valuable resources are discarded.

Repeating the final liquid in the smelting process is synonymous with processing a dilute raw material liquid, and there is a problem in terms of processing cost. In addition, ruthenium and the like gradually accumulate in the system, so it is desirable to recover them at the final stage and treat them in the ruthenium recovery step.

In view of such conventional circumstances, the present invention efficiently precipitates and separates selenium, ruthenium and / or tellurium from an acidic hydrochloric acid solution containing selenium and one or two of ruthenium and tellurium. Provide a method for recovering valuable resources.

As a result of intensive research to solve the above problems, the present inventors added a water-soluble ketone to the hydrochloric acid acidic solution, stirred until the hydrochloric acid acidic solution became turbid, and then supplied reducing sulfur to the hydrochloric acid acidic solution. It has been found that the precipitation of valuable resources containing selenium and ruthenium and / or tellurium can be efficiently obtained. The present invention has been completed based on such findings.

In one aspect, the present invention completed based on the above findings includes a step of adding a water-soluble ketone to a hydrochloric acid acidic solution containing selenium and one or two of ruthenium and tellurium, and the water-soluble ketone. The step of stirring until the turbid hydrochloric acid acidic solution becomes turbid, and the reducing sulfur is supplied to the turbid hydrochloric acid acidic solution to contain selenium and one or two of ruthenium and tellurium. It is a method of recovering valuables including a step of obtaining a precipitate of valuables and a step of recovering the precipitated valuables.

In one embodiment of the method for recovering valuable resources of the present invention, the water-soluble ketone is acetone or 2-butanone.

In another embodiment of the method for recovering valuable resources of the present invention, the reducing sulfur is supplied by adding the water-soluble ketone so that the ruthenium concentration in the hydrochloric acid acidic solution is before the water-soluble ketone is added. It starts when the initial concentration of is reduced to 95% or less.

In still another embodiment of the method for recovering valuable resources of the present invention, the water-soluble ketone is added so as to be 1 mL or more with respect to 1 L of the hydrochloric acid acidic solution.

In yet another embodiment of the method for recovering valuable resources of the present invention, the amount of the water-soluble ketone added is 2 mol times or more that of ruthenium or tellurium.

In yet another embodiment of the method for recovering valuable resources of the present invention, the reducing sulfur is at least one of sulfur dioxide, sulfite, sulfite, hydrogen sulfide and thiosulfuric acid.

According to the present invention, a method for efficiently precipitating and separating selenium, ruthenium and / or tellurium from an acidic hydrochloric acid solution containing selenium and one or two of ruthenium and tellurium to recover valuable resources. Can be provided.

Electrolytic slimes produced in the electrolytic refining process of non-ferrous metal smelting, especially copper smelting, are rich in chalcogen elements and precious metals. As an example, gold is 10 to 30 kg / t, silver is 100 to 250 kg / t, palladium is 1 to 3 kg / t, platinum is 200 to 500 g / t, tellurium is 15 to 25 kg / t, and selenium is 5 to 15 wt%. Contains about.

It also contains 100 to 250 g / t of iridium, 800 to 3000 g / t of ruthenium, and 30 to 100 g / t of rhodium as rare metals.

Hydrochloric acid and hydrogen peroxide are added to dissolve this electrolytic slime, but silver forms an insoluble silver chloride precipitate with chloride ions immediately after dissolution. If it is a solution containing an oxidizing agent and chlorine, for example, aqua regia or chlorine water, the precious metals can be dissolved and silver can be separated as silver chloride. Since it is a chloride bath, precious metal elements, rare metal elements, selenium, ruthenium, and tellurium are distributed in the pregnant leached solution (PLS).

The PLS is cooled once to precipitate and separate chlorides of base metals such as lead and antimony. After that, the gold is separated into an organic phase by solvent extraction. Dibutyl carbitol (DBC) is widely used as a gold extractant.

Valuables can be precipitated and recovered by reducing PLS after extracting gold, but the order of precipitation is naturally determined because the redox potential differs depending on the element. First, precious metals, then chalcogens such as selenium and tellurium, and then the inert noble metals are precipitated.

After recovering the precious metals, selenium is reduced and recovered. Reducing sulfur is used as the reducing agent in terms of price and efficiency, and sulfur dioxide is most suitable because it can be supplied in large quantities and at low cost by roasting linz-Donaw gas or sulfide ore. From the viewpoint of recovering high-purity selenium, selenium is not completely recovered, and the liquid after recovering selenium contains 2 to 4 g / L of selenium. The liquid after selenium recovery also contains 100 to 250 mg / L of ruthenium and 200 to 800 mg / L of tellurium.

After recovering selenium, reducing sulfur is blown into the liquid (hydrochloric acid acidic liquid) to recover valuable resources remaining in the liquid. In the conventional method, sulfur dioxide is blown by heating to 80 ° C. or higher. In the present invention, a water-soluble ketone is added to the hydrochloric acid acidic solution before blowing the sulfur dioxide (before supplying the reducing sulfur).

A small part of the ketone exists as an enol due to keto-enol tautomerization. It is considered that reduction occurs when the instantaneously generated π electron of enol moves to selenium or ruthenium. Alternatively, it is possible to enhance the reducing ability of sulfur dioxide by moving the π electron of the enol to sulfur dioxide to generate an anion radical. Tellurium and other valuable resources are reduced by the reducing ability of anion radicals.

Any of the ketones is effective, but the water-soluble ketones have high reaction efficiency and the increase in COD (chemical oxygen demand) in wastewater is not high, so that the water-soluble ketones having a small number of carbon atoms are preferable. Specific examples thereof include acetone and 2-butanone.

Tellurous acid is tetravalent, and since tetravalent selenous acid is also reduced with acetone, the reagent cost is increased by reduction with acetone alone. In order for acetone to act only as a reducing trigger, reducing sulfur is also supplied. Examples of reducing sulfur include sulfur dioxide, sulfurous acid, sulfites, hydrogen sulfide, and thiosulfuric acid. It is known that all compounds reduce tellurium and selenium to zero valence if conditions are met.

When sulfur dioxide is used in combination as the reducing sulfur, the amount of the water-soluble ketone added can be 1 mL or more, preferably 1 to 40 mL with respect to 1 L of the hydrochloric acid acidic solution. Although it depends on the composition of the reaction solution, the effect is high if the water-soluble ketone is 2 mol times or more the amount of substance of ruthenium or tellurium. If the amount added is too large, the cost will increase, the wastewater treatment will be burdened, and the evaporated ketones will worsen the working environment. On the contrary, if it is too small, the reaction will be slow.

Ruthenium is gradually reduced by water-soluble ketones. Reduction with sulfur dioxide alone has a slower reaction rate. By using a water-soluble ketone and sulfur dioxide in combination, the reduction reaction is promoted if both react to generate an anion radical.

On the other hand, ruthenium is particularly difficult to reduce under the condition that tellurous acid coexists. As a phenomenon observed at this time, tellurous acid is reduced and the concentration tends to decrease significantly, and at the same time, the concentration of ruthenium tends to decrease. From this, it is hypothesized that tellurium is coordinated to the first coordination sphere of ruthenium in the chloride bath, which hinders reduction. It is presumed that the tellurous acid coordinated to tellurium during tellurium reduction undergoes reduction at the moment when a vacancy is formed, or that it becomes more susceptible to reduction due to ligand exchange between enol and tellurous acid. A ruthenium complex in which all ligands are chloride ions is relatively stable and gradually undergoes reduction.

In order to efficiently reduce ruthenium, it is necessary to supply ketone and reducing sulfur, but it is important to supply reducing sulfur after ligand exchange with ketone. Therefore, reducing sulfur is supplied after adding a ketone and stirring sufficiently. This is because reducing sulfur contains sulfur, which is a relatively soft element, and interacts with the π electron of the enol to reduce its effect.

The timing of supply of reducing sulfur is detected by the change in the reaction solution. If it reacts sufficiently, fine particles are generated in the liquid and turbidity occurs. It is necessary to stir the hydrochloric acid acidic solution until such turbidity occurs in the hydrochloric acid acidic solution to which the water-soluble ketone is added. The time required for this turbidity to occur varies depending on the temperature and liquid composition, but is about 5 to 30 minutes, and if detected by turbidity, it is when the transmittance is 95% or less with visible light. That is, the supply of reducing sulfur can be started when the ruthenium concentration in the hydrochloric acid acidic solution drops to 95% or less of the initial concentration before the addition of the water-soluble ketone by adding the water-soluble ketone.

There are no particular restrictions on the amount or rate of supply of reducing sulfur. The precipitated precipitate is solid-liquid separated by a filter press or the like. Precipitates include ruthenium, selenium, tellurium, and precious metals.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited thereto.

(Example 1)
Copper was removed from the electrolytic slime recovered from copper smelting with sulfuric acid. Concentrated hydrochloric acid and 60% hydrogen peroxide solution were added and dissolved, and solid-liquid separation was performed to obtain an leaching noble liquid (PLS). The PLS was cooled to 6 ° C. to precipitate and remove base metals. Gold was extracted by mixing DBC (dibutyl carbitol) and PLS.
The PLS after gold extraction was heated to 70 ° C., and the exhaust gas from a copper smelting converter was blown in to reduce the noble metal and separate it into solid and liquid. The separated solution was heated again to 70 to 75 ° C. and the exhaust gas from the copper smelting converter was blown into it. The crude selenium was separated and recovered by solid-liquid separation. Table 1 shows each main component of the liquid after selenium separation.
After separating selenium, 300 mL of the liquid was taken. The mixture was heated to 70 to 75 ° C., 1 mL of acetone was added, and the mixture was stirred for 15 minutes (Example 1) and for 30 minutes (Example 2). 0.5 mL of acetone was added, and the mixture was stirred for 15 minutes (Example 3) and for 30 minutes (Example 4). After confirming that turbidity had occurred, a mixed gas of sulfur dioxide and air (sulfur dioxide concentration 5 to 20%) was blown at 0.1 L / min. The liquid was collected at regular intervals and the slurry was separated into solid and liquid. The solution was diluted 25-fold with dilute hydrochloric acid, and the concentrations of various components were measured by ICP-OES (SPS-3100 manufactured by Seiko Corporation). The measurement was carried out using yttrium as an internal standard element. The experimental results are shown in Table 2. In Table 2, the increase in concentration with the elapsed time is also due to the effect of liquid evaporation.

(Comparative Example 1)
A selenium-separated liquid having the composition shown in Table 1 was prepared by the same operation as in the examples.
For comparison, a mixed gas of sulfur dioxide and air was immediately blown into the same solution as in the example after addition of acetone. The amount of acetone added was 1 ml (Comparative Example 1) and 10 ml (Comparative Example 2). Instead of acetone, 1 ml of 2-butanone (Comparative Example 3), no addition (Comparative Example 4), and 10 ml of 2-propanol (Comparative Example 5) were added.
Further, after blowing a mixed gas of sulfur dioxide and air for 30 minutes, 1 ml (Comparative Example 6) and 10 ml (Comparative Example 7) of acetone were added, and the mixture was continuously reduced with a mixed gas of sulfur dioxide and air. Various concentrations in the liquid were quantified by the same operation as in the examples. The experimental results are shown in Table 3. In Table 3, the increase in concentration with the elapsed time is also due to the effect of liquid evaporation.

Comparative Example 4 is a system in which sulfur dioxide is reduced without addition, and the most notable point is how much the concentration of expensive ruthenium decreased after 3 hours. If tellurium is infused with sulfur dioxide for a long time, it will be reduced after the selenium concentration is sufficiently lowered, so the effect on tellurium should be focused on the reaction rate.

In each of the examples, the addition of acetone contributes to the reduction of ruthenium and tellurium. Even 0.5 ml was effective against 300 ml of the target solution. On the other hand, as seen in Comparative Example 6 and Comparative Example 7, if sulfur dioxide is sufficiently supplied before acetone acts on selenium, the effect is greatly diminished even if an excessive amount of acetone is added. Further, as seen in Comparative Example 1 and Comparative Example 2, even if the supply of sulfur dioxide is started at the same time as the addition of acetone, the effect is recognized, but the required amount increases.

From the results of Comparative Example 3 and Comparative Example 5, it can be seen that the ketone contributes to the reduction. Acetone is considered to have the same effect with other ketones, but acetone is the most superior in terms of low toxicity and solubility in water.

Regarding the amount of acetone added, the concentration of ruthenium has an effect in addition to the amount of noble liquid. The ruthenium concentration and the tellurium concentration were relatively high in both the examples and the comparative examples. Acetone showed an effect on ruthenium at 0.5 ml, which corresponds to 6.8 mmol of acetone against 2.9 mmol of ruthenium. The effect was shown by the addition of about 2 mol times or more.

Claims (6)

A step of adding a water-soluble ketone to an acidic hydrochloric acid solution containing selenium and one or two of ruthenium and tellurium.
The step of stirring until the hydrochloric acid acidic solution to which the water-soluble ketone is added becomes turbid, and
A step of supplying reducing sulfur to the turbid hydrochloric acid acidic solution to obtain a precipitate of valuable resources containing selenium and one or two of ruthenium and tellurium.
The step of collecting the precipitated valuable resources and
A method of collecting valuable resources. The method for recovering valuable resources according to claim 1, wherein the water-soluble ketone is acetone or 2-butanone. The supply of the reducing sulfur is characterized by starting when the ruthenium concentration in the hydrochloric acid acidic solution drops to 95% or less of the initial concentration before the addition of the water-soluble ketone by adding the water-soluble ketone. The method for collecting valuable resources according to claim 1 or 2. The method for recovering valuable resources according to any one of claims 1 to 3, wherein the water-soluble ketone is added so as to be 1 mL or more with respect to 1 L of the acidic hydrochloric acid solution. The method for recovering valuable resources according to any one of claims 1 to 4, wherein the amount of the water-soluble ketone added is 2 mol times or more that of ruthenium or tellurium. The method for recovering valuable resources according to any one of claims 1 to 5, wherein the reducing sulfur is at least one of sulfur dioxide, sulfite, sulfite, hydrogen sulfide and thiosulfuric acid. ..