JP6060877B2 - Method for producing rhenium-containing solution - Google Patents

Description

  The present invention relates to a method for producing a rhenium-containing solution containing only rhenium by treating a cleaning effluent discharged from an exhaust gas cleaning process of metal smelting using copper ore or molybdenum ore as a raw material.

Rhenium is a rare metal used as an additive element and catalyst for special alloys, and is naturally contained in molybdenite (MoS ₂ ), which is a raw material of molybdenum. In the smelting process of molybdenum, oxidation roasting of molybdenite is performed to solubilize molybdenum. At this time, rhenium contained in the molybdenite is separated from the molybdenite as a volatile oxide Re ₂ O ₇ , recovered in a scrubber or other cleaning process, and then purified.

It is known that pyroxenite coexists with copper minerals such as chalcopyrite (CuFeS ₂ ). Have difficulty. Therefore, in the process of obtaining copper from chalcopyrite by dry smelting using a furnace such as a blast furnace located in the subsequent stage of flotation, pyroxenite is also charged into the furnace at the same time. As a result, volatilized rhenium is mixed in the exhaust gas mainly composed of sulfurous acid gas discharged from the furnace.

  In addition to the above rhenium, arsenic contained in copper ore, volatilized or scattered copper, zinc, cadmium, and the like are solid or liquid fine particles (also called fumes). Floating). In order to remove these impurities, the exhaust gas is washed with a scrubber or the like as a pretreatment in the sulfuric acid production process. Since rhenium contained in the exhaust gas is also separated by this washing treatment, it has been difficult to efficiently recover only rhenium from the washing wastewater containing many kinds of elements described above.

  Therefore, as a method for selecting and separating only rhenium from a solution in which a plurality of elements coexist, a separation method using an anion exchange resin has been proposed. For example, in Patent Document 1, hydrogen sulfide gas is blown in a state in which the sulfuric acid concentration is maintained at 70 g / L or more with respect to the cleaning effluent discharged from the cleaning process of the sulfurous acid gas generated in the smelting process of nonferrous metal. Alternatively, a soluble sulfide is added, a sulfide containing rhenium is precipitated under the condition of an oxidation-reduction potential of 120 to 150 mV (vs. silver-silver chloride electrode), and the resulting sulfide precipitate is sulfuric acid in an acidic aqueous solution. Mixing with copper to form an aqueous solution containing rhenium, bringing the aqueous solution containing rhenium into contact with a quaternary ammonium salt anion exchange material to selectively adsorb and recover rhenium. A recovery method is disclosed.

  In addition, as a separation method that does not use an anion exchange resin, in Patent Document 2, iron ions are added to a perrhenic acid solution in which arsenic coexists, and then air is blown into the liquid as an oxidizing agent to trivalent arsenic. Is disclosed in which arsenic is removed from starch by oxidation to pentavalent ions and alkali neutralization at pH 9-10.

JP 7-286221 A International Publication No. 2013/129130 Pamphlet

  However, since the method of Patent Document 1 uses an aqueous ammonium thiocyanate solution to elute rhenium adsorbed on the anion exchange resin, it has a problem that toxic cyanide ions are generated when the ammonium thiocyanate is decomposed. It was. In addition, wastewater containing a compound in which ammonium thiocyanate is decomposed has a problem in that the chemical oxygen demand (COD) and nitrogen concentration are high, so that the environmental load is large and wastewater treatment costs are high.

  Furthermore, the process using an anion exchange resin, for example, when refining a molybdenum smelting step or a waste catalyst containing rhenium, when the rhenium quality in the raw material is relatively high and stably contained. Although it can be applied without any problem, it often becomes a problem when the concentration of rhenium varies. For example, when recovering rhenium produced as a by-product of copper smelting, the rhenium quality in the raw copper ore may vary by up to 10 times.

  Along with this variation, the rhenium concentration in the aqueous solution supplied to the process using the anion exchange resin also varies greatly. In the process using an anion exchange resin, the contact step of bringing the liquid containing rhenium to be separated into contact with the anion exchange resin takes the longest time. Therefore, when the contact process requiring the longest time is designed based on the conditions when the rhenium concentration in the liquid is the highest, the equipment becomes large and the cost is high.

  Moreover, since the method of patent document 2 oxidizes arsenic by blowing air in a liquid as an oxidizing agent, it required 10 hours or more for oxidation. For this reason, in order to process a large amount of solution, a large-scale facility is required, and in this case as well, the cost is problematic. The present invention has been made in view of the above-described conventional problems, and separates an impurity element from an aqueous solution containing an impurity element such as arsenic in a short time without requiring a large-scale facility, and a rhenium sulfide process. It aims at providing the method of manufacturing the rhenium containing solution used as the raw material of this.

  In order to achieve the above object, the method for producing a rhenium-containing solution of the present invention is such that the molar ratio of divalent metal ions to arsenic ions in a solution containing at least arsenic and perrhenic acid is greater than 3. A first step of adding the source material of the divalent metal ion to the solution; a second step of adding an alkali agent to the solution obtained in the first step to adjust the pH to 7.0 or more and less than 9.0; And a third step of adjusting the oxidation-reduction potential to -100 mV or higher and +100 mV or lower by adding a liquid or solid oxidizing agent to the solution obtained in the second step.

  In the method for producing a rhenium-containing solution of the present invention, it is preferable that the addition of the divalent metal ion source material is addition of at least one of ferrous sulfate and ferrous chloride. The alkaline agent is preferably at least one of sodium hydroxide and sodium carbonate. Furthermore, the oxidizing agent is preferably at least one of an aqueous potassium permanganate solution, a hydrogen peroxide solution, and activated carbon.

  According to the present invention, an impurity element is separated from an aqueous solution containing an impurity element such as arsenic in a short time without requiring a large-scale facility, and a rhenium-containing solution that is a raw material for the rhenium flow process is produced. A method can be provided.

It is a general block flow figure showing the manufacturing method of the rhenium content solution of one example of the present invention, and the method of collect | recovering rhenium from the rhenium content solution obtained by this method.

  Hereinafter, a specific example of the method for producing a rhenium-containing solution of the present invention will be described. The method for producing a rhenium-containing solution according to an embodiment of the present invention is intended for cleaning waste liquid discharged from a cleaning process of exhaust gas generated in a non-ferrous metal smelting process. This washing drainage contains at least arsenic and perrhenic acid. First, as a first step, a divalent metal ion source material is added to the cleaning effluent so that the molar ratio of divalent metal ions to As ions in the cleaning effluent is greater than 3. Thereby, a hardly soluble compound can be produced | generated from the arsenic in washing | cleaning drainage liquid.

The reason why the molar ratio of the divalent metal ion to the As ion in the washing effluent is larger than 3 is to produce a hardly soluble compound containing arsenic in a short time. That is, arsenic forms different salt forms depending on the ratio of metal ions, and divalent arsenate M (H ₂ AsO ₄ ) _{2 when} divalent metal ions such as iron are present in an amount of 0.5 mol or less relative to 1 mol of arsenic. (M: divalent metal) only is produced, and when it exceeds 0.5 mol and less than 1.0 mol, dihydrogen arsenate and monohydrogen arsenate MHAsO ₄ are produced, and at 1.0 mol, monohydrogen arsenate. Only when it exceeds 1.0 mol and less than 1.5 mol, monohydrogen arsenate and arsenate M ₃ (AsO ₄ ) ₂ are generated, and when it is 1.5 mol or more, only arsenate is generated.

  Of these compounds, only monohydrogen arsenate and arsenate are salts that are difficult to dissolve in water. Therefore, when only these poorly soluble compounds are to be produced, the moles of divalent metal ions relative to arsenic ions in the liquid The ratio needs to be 1 or more. Furthermore, in order to obtain these hardly soluble monohydrogen arsenate and arsenate in a short time, the molar ratio of the divalent metal ion to the arsenic ion needs to be larger than 3.

  The divalent metal ion is preferably a divalent iron ion. In this case, the source material of the divalent iron ions is added to the cleaning waste liquid so as to have the above molar ratio. The divalent iron ion source material is preferably an iron compound that is not sparingly soluble. Specifically, at least one of ferrous sulfate and ferrous chloride having relatively high solubility may be used. preferable.

  Next, as a second step, an alkaline agent is added to the solution containing the poorly soluble compound obtained in the first step to adjust the pH to 7.0 or more and less than 9.0. Thereby, more hydrogen arsenate and arsenate can be produced | generated, and also the production | generation of this poorly soluble compound can be stabilized by suppressing re-dissolution of the already poorly soluble compound. When this pH is less than 7.0, the formation of monohydrogen arsenate and arsenate which are hardly soluble compounds becomes insufficient. On the other hand, when this pH is 9.0 or more, re-dissolution becomes remarkable in arsenates other than monohydrogen arsenate and Fe, and the As concentration in the liquid increases.

  In general, when heavy metals are removed from the liquid by producing hydroxide, the pH is 9 to 10 for cadmium and 10 to 12 for zinc. However, since cadmium and zinc are also removed by coprecipitation with iron or precipitation with arsenate, the pH is 7.0 or higher, which is lower than the pH at the time of formation of the above-mentioned general hydroxides. Even if it is less than 0, cadmium and zinc can be sufficiently removed.

  It is preferable that the alkaline agent added in the second step is not hardly soluble in the aqueous solution. Specifically, at least one of sodium hydroxide and sodium carbonate having relatively high solubility is used. Is preferred.

  Next, as a third step, a liquid or solid oxidant is added to the aqueous solution containing the poorly soluble compound obtained in the second step so that the oxidation-reduction potential is −100 mV to 100 mV. This makes it possible to oxidize trivalent arsenic remaining in the liquid to become pentavalent without becoming a hardly soluble compound, and to increase more difficultly soluble compounds such as monohydrogen arsenate and arsenate. Can be generated. Further, trivalent arsenic existing in an aqueous solution after being partly redissolved can be made into a hardly soluble compound by being oxidized in this third step to become pentavalent.

  When this oxidation-reduction potential is less than −100 mV, the ratio of pentavalent arsenic in the aqueous solution decreases, and it is difficult to obtain monohydrogen arsenate and arsenate which are hardly soluble compounds. On the other hand, even if a liquid or solid oxidizing agent is added so that the oxidation-reduction potential exceeds 100 mV, most of arsenic in the aqueous solution is already pentavalent, and monohydrogen arsenate, which is a poorly soluble compound, The effect of obtaining arsenate is almost unchanged.

  In the third step, it is required to add a liquid or solid oxidant. The reason is that when oxidizing arsenic in the liquid, when a gaseous oxidant such as air is blown, the oxidant in the bubbles must react with the arsenic in the liquid. Therefore, in order to promote the reaction efficiently, it is necessary to blow as fine bubbles as possible into the aqueous solution. However, it is very difficult to generate fine bubbles and blow them so as to spread throughout the industrial reaction tank.

  On the other hand, in the case of a liquid oxidizer, simply adding a liquid oxidizer to the reaction tank and stirring it using a stirrer generally provided in the reaction tank makes it easy and efficient. The reaction can proceed. In the case of a solid oxidizer, if necessary, the solid oxidizer is pulverized by pulverization or the like and then put into a reaction vessel. Similarly, the reaction can be carried out easily and efficiently simply by using a stirrer. Can proceed. For example, when potassium permanganate is used as the liquid oxidizing agent, the oxidation reaction is almost completed in about 1 hour. On the other hand, when air is used as a gaseous oxidant, it takes 10 hours or more to oxidize to the same extent.

  The liquid or solid oxidizing agent added in the third step may be any liquid or solid oxidizing agent as long as it can be uniformly dispersed in the aqueous solution. It is preferable to use at least one of an aqueous potassium solution, a hydrogen peroxide solution, and activated carbon. This is because the potassium permanganate aqueous solution, the hydrogen peroxide solution, and the activated carbon are easily available and easy to handle. In addition, when activated carbon is added, activated carbon acts as a catalyst and acts in the same way as an oxidizing agent.

  By removing solids such as arsenic, cadmium and zinc obtained through the above-described first to third steps by solid-liquid separation, an aqueous solution containing substantially only rhenium as a solute is obtained. . For example, as shown in FIG. 1, a sulfurizing agent such as sodium hydrosulfide and sulfuric acid are added to the rhenium-containing solution thus obtained to perform a sulfurization reaction. As a result, a precipitate of rhenium sulfide can be generated, so that rhenium can be recovered as rhenium sulfide by solid-liquid separation.

Example 1
The cleaning effluent discharged from the exhaust gas cleaning process of the metal refining plant was collected to prepare an aqueous solution containing an arsenic concentration of 18.5 g / L and rhenium 2.1 g / L as perrhenic acid. As a first step for this aqueous solution, ferrous sulfate was added to the aqueous solution so that the molar ratio of iron ions to arsenic ions (Fe / As) in the aqueous solution was 3.1. Next, as a second step, an aqueous solution of sodium hydroxide having a concentration of 8 mol / L was added to the aqueous solution obtained in the first step to adjust the pH to 8.9.

  Further, as the third step, a potassium permanganate solution having a concentration of 20 g / L is applied to the aqueous solution obtained in the second step until the measured value at the reference electrode of the silver-silver chloride electrode becomes -100 mV. Added. Finally, the aqueous solution obtained in the third step was filtered to separate the filtrate and the precipitate. As a result, the third step took only 1.0 hour. Moreover, when the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.97%.

(Example 2)
Same as Example 1 except that the pH was adjusted to 7.0 in the second step and that the potassium permanganate solution was added until the redox potential was +100 mV in the third step. As a result, the third step took only 1.5 hours. Moreover, when the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.98%.

Example 3
Example 3 was performed in the same manner as in Example 1 except that 30% hydrogen peroxide solution was added until the oxidation-reduction potential reached −100 mV in the third step. As a result, the third step took only 1.0 hour. Moreover, when the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.96%.

Example 4
The same procedure as in Example 1 was performed except that powdered activated carbon having a particle size of less than 150 μm was added until the oxidation-reduction potential became −100 mV in the third step. As a result, the third step took only 1.0 hour. Moreover, when the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.90%.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that air bubbling was performed at a flow rate of 2.0 L / min until the oxidation-reduction potential became −10 mV in the third step. As a result, the third step took 16 hours. Moreover, when the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.80%.

  As can be seen by comparing the results of Examples 1 to 4 and the result of Comparative Example 1, when an impurity element such as arsenic is separated from the cleaning effluent based on the requirements of the present invention, it contains rhenium efficiently in a short time. A solution could be obtained. On the other hand, when an impurity element such as arsenic was separated from the same washing waste solution by a method that was not required by the present invention, the treatment took time and the arsenic precipitation rate was inferior.

Claims (4)

A first step of adding a source material of the divalent metal ion to the solution such that the molar ratio of the divalent metal ion to the arsenic ion in the solution containing at least arsenic and perrhenic acid is greater than 3.
A second step in which an alkaline agent is added to the solution obtained in the first step to adjust the pH to 7.0 or more and less than 9.0;
And a third step of adjusting the oxidation-reduction potential to -100 mV or more and +100 mV or less by adding a liquid or solid oxidant to the solution obtained in the second step.   The method for producing a rhenium-containing solution according to claim 1, wherein the addition of the divalent metal ion source material is addition of at least one of ferrous sulfate and ferrous chloride.   The method for producing a rhenium-containing solution according to claim 1 or 2, wherein the alkaline agent is at least one of sodium hydroxide and sodium carbonate.   The rhenium-containing solution according to any one of claims 1 to 3, wherein the oxidizing agent is at least one of an aqueous potassium permanganate solution, a hydrogen peroxide solution, and activated carbon. Manufacturing method.

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