JP2015094013A - Method of producing rhenium-containing solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a rhenium-containing solution, a raw material for rhenium purification processes, safely and at low costs even when the quality of rhenium varies significantly.SOLUTION: A method of producing a rhenium-containing solution includes a first step of adding a divalent metal ion supply source substance, preferably ferrous sulfate and/or ferrous chloride, to a solution containing arsenic and perrhenic acid, in a molar ratio of the divalent metal ion to the arsenic ion in the solution of 1-3, a second step of adding an alkali agent, e.g. sodium hydroxide, to the solution obtained in the first step to a pH of 7.0 or higher and lower than 9.0 and a third step of air-bubbling the solution obtained in the second step to adjust the oxidation-reduction potential to -100 to +100 mV.

Description

  The present invention relates to a method for producing a rhenium-containing solution that substantially contains only rhenium by treating the cleaning effluent discharged from the exhaust gas cleaning process in copper smelting.

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 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.

JP-A-7-286221

  However, since the method of Patent Document 1 uses an ammonium thiocyanate aqueous solution when eluting 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 producing rhenium produced as a by-product of copper smelting, the rhenium quality in the raw copper ore may vary 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.

  The present invention has been made in view of the above-described conventional problems, and even when the rhenium quality greatly fluctuates, such as a copper smelting process, it is safe and inexpensive regardless of the process using the anion exchange resin. It aims at providing the method of manufacturing the rhenium containing solution used as the raw material of a rhenium fluidization process.

  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 1 or more and 3 or less. A first step of adding the divalent metal ion source material to the solution, and 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 to +100 mV by air bubbling the solution obtained in the second step.

  In the above-described method for producing a rhenium-containing solution of the present invention, the addition of the divalent metal ion source material is preferably addition of at least one of ferrous sulfate and ferrous chloride. Moreover, it is preferable that an alkaline agent is at least one of sodium hydroxide and sodium carbonate.

  According to the present invention, a rhenium-containing solution that can be used as a raw material for a rhenium fluidization process safely and at low cost, regardless of the process using an anion exchange resin, even when the rhenium quality varies greatly, such as a copper smelting process. 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 supply 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 1 or more and 3 or less. 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 1 or more and 3 or less is that the poorly soluble compound containing arsenic can be stably stabilized even when the rhenium quality varies greatly. It is for generating. That is, arsenic forms different salt forms depending on the ratio of metal ions, and divalent arsenate M (H ₂ AsO ₄ ) when divalent metal ions such as iron are present at 0.5 mol or less per 1 mol of arsenic. ₂ (M: divalent metal) 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 salt is produced, and when it exceeds 1.0 mol and less than 1.5 mol, monohydrogen arsenate and arsenate M ₃ (AsO ₄ ) ₂ are produced, and only 1.5 arsenate is produced at 1.5 mol or more. .

  Among these compounds, only monohydrogen arsenate and arsenate form salts that are difficult to dissolve in water. Therefore, when only these poorly soluble compounds are to be produced, divalent metal ions with respect to arsenic ions in the liquid It is necessary to make the molar ratio 1 or more. On the other hand, it was found that a molar ratio of divalent metal ions to arsenic ions of 3 or less was sufficient to ensure an appropriate removal rate.

  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 production of monohydrogen arsenate and arsenate, which are hardly soluble compounds, becomes insufficient. On the other hand, when this pH is 9.0 or more, redissolution starts with arsenate 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, air bubbling is performed on the aqueous solution containing the poorly soluble compound obtained in the second step so that the oxidation-reduction potential is −100 mV or more and +100 mV or less. 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 air bubbling is performed so that the oxidation-reduction potential exceeds +100 mV, most of the arsenic in the aqueous solution is already pentavalent, and monohydrogen arsenate and arsenate which are hardly soluble compounds are obtained. The effect is almost unchanged.

  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. 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 7.0.

  Further, as the third step, air bubbling is performed at a flow rate of 2.0 L / min until the measured value at the reference electrode of the silver-silver chloride electrode becomes -100 mV for the aqueous solution obtained in the second step. went. Finally, the aqueous solution obtained in the third step was filtered to separate the filtrate and the precipitate. When the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.9%.

(Example 2)
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 as a cleaning liquid and 0.2 g / L of rhenium as perrhenic acid. First, ferrous sulfate was added to the aqueous solution so that the molar ratio (Fe / As) of iron ions to arsenic ions in the aqueous solution was 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, the aqueous solution obtained in the second step is subjected to air bubbling at a flow rate of 2.0 L / min until the measured value at the reference electrode of the silver-silver chloride electrode becomes +100 mV. It was. Finally, the aqueous solution obtained in the third step was filtered to separate the filtrate and the precipitate. When the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.8%.

(Comparative Example 1)
As the second step, ferrous sulfate was added so that the molar ratio (Fe / As) of iron ions to arsenic ions in the aqueous solution was 0.9 as the first step with respect to the same washing drainage as in Example 1. The pH was adjusted to 6.0, and 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 −110 mV as the third step. When the precipitation rate of each component was computed from the analysis value of the deposit and the filtrate, the arsenic precipitation rate was 99.0%.

  From the results of Examples 1-2 above, when an impurity element such as arsenic was separated from the cleaning effluent based on the requirements of the present invention, arsenic or the like even when the rhenium concentration in the cleaning effluent greatly fluctuated It can be seen that a high-purity rhenium-containing solution containing substantially only rhenium can be obtained by removing the impurities. On the other hand, it can be seen from the results of Comparative Example 1 that a high-purity rhenium-containing solution cannot be obtained when an impurity element such as arsenic is separated from the same cleaning effluent by a method deviating from the requirements of the present invention.

Claims (3)

A first step of adding a source material of the divalent metal ion to the solution so that the molar ratio of the divalent metal ion to the arsenic ion in the solution containing at least arsenic and perrhenic acid is 1 or more and 3 or less; ,
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 higher and +100 mV or lower by air bubbling 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.

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