JP2011058016A - Method for separating rhenium from solution containing perrhenic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive method, even if the content of rhenium in raw material is remarkably varied, which can stably and efficiently separate rhenium. <P>SOLUTION: In the method for separating rhenium from a solution containing one or more elements selected from copper, zinc, cadmium and arsenic, and perrhenic acid, the method comprises: a first stage 1 where alkali such as sodium hydroxide is added to the solution so as to produce precipitates, and the solution containing the precipitates is subjected to solid-liquid separation by a separation process such as filtration; a second stage 2 where acid such as sulfuric acid is added to a separated liquid obtained by the solid-liquid separation, and the concentration of the acid is regulated to a range satisfying the equivalent concentration of 1.0 to 4.0 normal; and a third stage 3 where a sulfurizing agent such as sodium hydrogensulfide is added to the regulation liquid obtained by the addition of the acid so as to produce sulfide precipitates, and the sulfide precipitations are separated from the liquid after the sulfurization. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for separating rhenium from a mixed aqueous solution containing rhenium and non-ferrous metal ions produced in the process of smelting a non-ferrous metal sulfide mineral. In particular, the present invention relates to a method for separating rhenium when rhenium is present as perrhenic acid in a mixed aqueous solution.

It is known that rhenium (Re) exists in nature by being mainly contained in molybdenite (MoS ₂ ). In the process of smelting molybdenum from such molybdenite, oxidation roasting treatment of molybdenite ore is performed for the purpose of solubilizing molybdenum. It is separated from molybdenite as a reactive oxide Re ₂ O ₇ , recovered with a scrubber or the like and purified.

In addition, it is also known that pyroxenite coexists with copper minerals such as chalcopyrite (CuFeS ₂ ). It is also known that when pyroxenite coexists with chalcopyrite, it is difficult to separate them from each other by a method such as flotation.

  Therefore, when copper is obtained from chalcopyrite using dry smelting method, when chalcopyrite is charged into the furnace and melted and smelted, hydropyrite ore is also charged into the furnace at the same time. Rhenium contained in molybdenite is volatilized and is collected in the cleaning liquid in the exhaust gas cleaning process for recovering the generated gas. At that time, metal fumes such as arsenic, copper, zinc, and cadmium coexisting in the copper ore are also volatilized or scattered and collected in the above-described cleaning process, so that the cleaning liquid contains various impurities.

  By the way, in the case of separating rhenium from a solution, for example, there is a method of adding a sulfurizing agent to the solution to sulfidize rhenium to obtain a sulfide precipitate and recover it. However, in the case of the cleaning liquid containing a wide variety of impurities as described above, impurities such as zinc and copper which are simultaneously present in the cleaning liquid tend to generate sulfides. Accordingly, it has been difficult to selectively recover only rhenium from cleaning liquids containing various impurities and efficiently recover them.

  Therefore, conventionally, in order to selectively separate rhenium from a solution in which a plurality of elements coexist, a method of separating rhenium or impurities by using an ion exchange resin has been used. For example, Patent Document 1 discloses a method for recovering rhenium from a non-ferrous metal smelting process by selectively adsorbing rhenium by bringing an aqueous solution containing rhenium into contact with an anion exchange material.

  Specifically, the sulfuric acid concentration of the sulfurous acid gas cleaning solution generated from the non-ferrous metal smelting process is maintained at 70 g / l or more, and hydrogen sulfide gas is blown into the sulfurous acid gas cleaning solution or a soluble sulfide is added. Then, a sulfide precipitate containing rhenium is generated under the condition of a redox potential of 120 to 150 mV (vs. silver-silver chloride electrode). Next, the sulfide precipitate is mixed with copper sulfate in an acidic aqueous solution to obtain an aqueous solution containing rhenium, and the obtained rhenium-containing aqueous solution is contacted with a quaternary ammonium salt anion exchange material to selectively select rhenium. Discloses a method of adsorbing and recovering.

  Patent Document 2 discloses a method for recovering platinum and rhenium from an alkaline aqueous solution obtained by leaching a waste catalyst containing platinum and rhenium with an alkaline solution. Specifically, platinum is separated by reducing an alkaline aqueous solution containing rhenium and platinum with ferrous sulfate, and the resulting aqueous solution is contacted with an anion exchange resin to adsorb and separate rhenium. Next, a hydrochloric acid solution having a concentration of 7 mol / l or more is passed through the anion exchange resin adsorbed with rhenium to elute rhenium from the anion exchange resin, and the hydrochloric acid concentration of the obtained eluent is 5 to 6. Adjust to 5 mol / l. Finally, a method is disclosed in which rhenium is separated as a rhenium sulfide produced by adding 1.5 times the equivalent amount of hydrogen sulfide to rhenium.

JP 7-286221 A JP 2006-130387 A

  However, the process using these ion exchange methods generally has a problem that the amount of capital investment is relatively large. For this reason, depending on the object to be processed, it is difficult to design and operate to increase production efficiency such as optimization of facility capacity. Specifically, in the case of recycling the smelting process of molybdenum or the waste catalyst containing rhenium, the rhenium quality in the raw material is relatively high and the content is stable, so this is not a big problem. On the other hand, when recovering rhenium produced as a by-product of copper smelting, the quality of rhenium in the copper ore used as a raw material is unstable and fluctuates greatly, so facilities that operate efficiently and at low cost should be designed and operated. Is not easy.

  Furthermore, in the method of Patent Document 1, an ammonium thiocyanide aqueous solution is used when eluting rhenium adsorbed on the anion exchange resin, so that ammonium thiocyanide may decompose to generate toxic cyanide ions. In addition, wastewater containing a compound in which ammonium thiocyanide is decomposed has a large impact on the environment such as high chemical oxygen demand (COD) and nitrogen concentration, and the cost of chemicals required to treat the wastewater is high. It also has the problem. Thus, the method of Patent Document 1 is not necessarily advantageous industrially.

  The method of Patent Document 2 uses hydrochloric acid having a concentration of 7 mol / l when eluting rhenium from the anion exchange resin, and the load on the environment is small compared to the method used in Patent Document 1. However, the method of Patent Document 2 is also a process centered on the ion exchange method, and since high concentration hydrochloric acid is used for elution and sulfidation, it is necessary to use materials with high corrosion resistance for the equipment. Challenges still remain.

  As described above, it was difficult to separate and recover rhenium stably and highly efficiently, particularly under conditions where the rhenium content fluctuates, such as a smelting process. In view of such conventional circumstances, an object of the present invention is to provide a low-cost method capable of stably and efficiently separating rhenium even if the content of rhenium in the raw material varies greatly.

  In order to solve the above problems, the rhenium separation method provided by the present invention is a method for separating rhenium from a solution containing one or more elements of copper, zinc, cadmium and arsenic and perrhenic acid. Then, an alkali is added to the solution to form a precipitate, and the solution containing the precipitate is subjected to solid-liquid separation, and an acid is added to the separated liquid obtained by the solid-liquid separation to obtain an equivalent concentration of 1 A second step of adjusting the concentration of the acid within a range of not less than 0.0 N and not more than 4.0 N, and adding a sulfiding agent to the adjustment liquid obtained by the addition of the acid to form a sulfide, And a third step of separating the solution from the liquid after sulfidation.

  In the rhenium separation method of the present invention, when arsenic coexists in the perrhenic acid-containing solution, a compound containing one or more elements of copper, zinc, and cadmium in advance is added at a molar concentration of arsenic. It is preferable to carry out the first to third steps after adding the above concentration.

  In the rhenium separation method of the present invention, it is preferable to adjust the amount of the alkali added so that the pH of the solution is 8 or more in the first step, and the adjustment in the third step. It is preferable to adjust the addition amount of the sulfiding agent so that the oxidation-reduction potential of the liquid is in the range of 0 mV or more and 50 mV or less as measured at the reference electrode of the silver-silver chloride electrode.

  According to the present invention, rhenium can be selectively separated basically by a neutralization treatment with an alkali and a sulfuration treatment without going through complicated steps. In addition, facilities that require significant investment and labor, such as ion exchange towers, are not required, and environmental burdens in wastewater treatment can be reduced. In addition, general-purpose materials can be used as the material of the equipment, so that costs can be reduced. . Furthermore, rhenium can be separated stably and efficiently against fluctuations in the rhenium quality in the raw material.

It is a schematic flowchart which shows one specific example of the separation method of rhenium based on this invention.

  Hereinafter, a specific example of the method for separating rhenium according to the present invention will be described with reference to the schematic flow chart of FIG. In general, when a metal is smelted by the above-described dry smelting method, rhenium contained in a raw material or the like is oxidized to rhenium oxide (VII), that is, rhenium heptoxide, and volatilizes easily. Volatilized rhenium oxide (VII) is collected in a cleaning liquid in a wet processing apparatus such as a scrubber as an exhaust gas together with other gas components. In this cleaning solution, it is known that rhenium (VII) oxide dissolves and exists as a stable perrhenic acid.

  In general, an aqueous solution containing metal ions such as copper, zinc, cadmium and lead forms a sulfide which is difficult to dissolve in water when a sulfurizing agent is added. Further, even when an alkali is added to the aqueous solution, a hardly soluble hydroxide is formed. As described above, the aqueous solution containing the metal ions has a property of generating a hardly soluble precipitate for both sulfides and hydroxides.

  In contrast, when rhenium is present in the form of the above-mentioned perrhenic acid, the perrhenic acid ion cationizes in the presence of the acid and forms a sulfide precipitate. The inventor has found that perrhenic acid has the property of not forming a precipitate of hydroxide or perrhenate. Furthermore, the present inventor has found that only rhenium can be selectively separated from all coexisting elements other than rhenium by combining treatments utilizing these properties.

  That is, by adding an alkali to a perrhenic acid-containing solution containing at least one element of copper, zinc, cadmium, and arsenic and perrhenic acid, as typified by the cleaning solution, hydroxides and the like Of the first step 1 in which the solution containing the precipitate is solid-liquid separated by a solid-liquid separation method such as filtration, and the separation liquid obtained by the solid-liquid separation in the first step 1 A second step 2 in which an acid is added to adjust the concentration of the acid within an equivalent concentration range of 1.0 N to 4.0 N, and a sulfiding agent is added to the adjustment liquid obtained by the addition of the acid in the second step 2. By adding the sulfurized precipitate by addition and the third step 3 for separating the sulfided precipitate from the post-sulfurized solution, rhenium can be efficiently separated from the rhenic acid-containing solution.

  In addition, when the above-mentioned exhaust gas is strongly reducing and rhenium in the cleaning liquid such as a scrubber is not oxidized, before performing the processing of the above-described first step 1 to third step 3, air or the like is added to the cleaning liquid. By oxidizing the cleaning solution by performing an oxidation treatment such as blowing an oxidizing agent, it can be easily converted into a perrhenic acid form.

  In this regard, the degree of redox potential and the like necessary to completely oxidize rhenic acid to perrhenic acid cannot be uniquely defined by liquidity. For example, in the vicinity of strong acidity where the pH value is 0, silver − Oxidation can be achieved by maintaining an oxidation-reduction potential of about 500 mV or higher with a silver chloride electrode as a reference electrode. Therefore, if the oxidation-reduction potential of the scrubber cleaning liquid is within this range from the beginning, there is no need to perform a new oxidation treatment.

  Copper ore often contains impurities such as arsenic as well as rhenium. In particular, arsenic is volatilized in the dry smelting process in the same manner as rhenium, and since it has the same behavior as rhenium, such as being collected in a cleaning solution by a scrubber, it is preferable to perform a process for separating arsenic and rhenium. The collected arsenic is known to exist in the form of arsenic acid or arsenous acid in the liquid, but these arsenic compounds are water in the alkaline region as in the case of perrhenic acid. Oxide precipitation does not occur, and it has the property of forming sulfide precipitates in the acidic region.

By the way, it is known that arsenic acid differs in the form of the generated salt depending on the ratio of the coexisting metal ions. For example, divalent metal ions M such as copper, zinc, cadmium and arsenic are dihydrogen arsenate (M (H ₂ AsO ₄ ) ₂ ), monohydrogen arsenate (MHAsO ₄ ), arsenate (M ₃ (AsO ₄ ) ₂ ) and the like, which are determined by the molar ratio of the above metal ions to arsenic.

Among the compounds described above, monohydrogen arsenate and arsenate have a property that they are difficult to dissolve in water. Therefore, when arsenic is present, before adding the above-mentioned alkali, if divalent metal ions are added to a concentration of 1 mol / l or more with respect to 1 mol / l of arsenic, the arsenic will become one of the above-mentioned arsenic acids. A hardly soluble form such as hydrogen salt (MHAsO ₄ ) or arsenate (M ₃ (AsO ₄ ) ₂ ) can be formed, and arsenic can be separated. Metal ions that have not been used to form compounds with arsenic precipitate when alkali is added and can be separated from rhenium.

  Although the perrhenic acid-containing solution is neutralized by the addition of alkali, it is preferable to adjust the amount of alkali added so as to maintain a predetermined pH value. For example, when completely separating cadmium that easily coexists with rhenium, it is necessary to maintain the pH at 8 or more. Moreover, since arsenic elutes from the precipitate when the pH exceeds 10, for example, when cadmium and arsenic are present, the above impurities can be reliably separated from rhenium by adjusting the pH to a range of 8 to 10. . Thus, the pH value that should be suitably maintained during neutralization varies slightly depending on the coexisting elements other than arsenic.

  The type of alkali is not particularly limited, and alkali metal or alkaline earth metal hydroxides, carbonates, ammonia, ammonium carbonate, and the like can be used. However, when the perrhenic acid concentration is high, potassium, rubidium, cesium, and ammonium ions tend to form perrhenate precipitates, and calcium, strontium, and barium compounds often contain sulfate ions and sulfates that coexist. There is a problem of forming a precipitate and increasing the precipitation volume. Moreover, it is not easy to adjust the pH of the solution to a relatively narrow range such as 8 or more, particularly 8 or more and 10 or less, by adding a magnesium compound or carbonate. For this reason, it is easy and most suitable to use sodium hydroxide.

  Slightly soluble precipitates such as hydroxides produced by the addition of the alkali are separated from the solution by solid-liquid separation methods such as filtration, centrifugation, and gravity sedimentation. The separation liquid obtained by this solid-liquid separation is subjected to sulfurization treatment.

  In the sulfiding treatment, it is necessary to coexist an acid in order to quantitatively obtain rhenium sulfide with respect to the added sulfiding agent. This is because the perrhenate ion has an anion form, and therefore, in order to cause sulfidation and precipitation, the perrhenate ion is first formed into a cation form as shown in the following chemical formulas 1 and 2. It is thought that it is necessary to change to.

[Chemical 1]
HReO ₄ + 7H ⁺ → Re ⁷⁺ + 4H ₂ O

[Chemical 2]
2Re ⁷⁺ + 7S ^2- → Re ₂ S ₇

  In the rhenium separation method of the present invention, as described above, since the neutralization treatment is performed in the first step 1, it is necessary to newly add an acid involved in the reaction of the above-mentioned chemical formula 1. Therefore, the acid is added in the second step 2 before the sulfiding treatment in the third step 3. As the kind of acid to be added, it is preferable to use a non-oxidizing acid which is a strong acid and does not decompose sulfides so that perrhenic acid is stably present. Specifically, an acid such as sulfuric acid or hydrochloric acid can be used. However, it is optimal to use sulfuric acid in consideration of cost, corrosiveness of apparatus material, volatility, and the like.

  In the case of sulfuric acid, since the reaction does not proceed when the sulfuric acid concentration is less than 0.5 mol / l, 0.5 mol / l or more is necessary. On the other hand, a sulfuric acid concentration exceeding 2.0 mol / l is not suitable because acid dissolution of the produced rhenium sulfide tends to proceed. In the case of hydrochloric acid, similarly, when the hydrochloric acid concentration is less than 1.0 mol / l, the reaction does not proceed easily, and when the hydrochloric acid concentration exceeds 4.0 mol / l, the acid dissolution of the produced rhenium sulfide is likely to proceed. Therefore, it is preferable to maintain the acid concentration in the range of 1.0 N to 4.0 N, preferably 2.0 N to 3.0 N in terms of equivalent concentration.

  In the third step 3, a sulfurizing agent is added to the adjustment solution obtained by the addition of the acid to precipitate rhenium as a sulfide, and then the sulfide precipitate is separated by solid-liquid separation such as filtration, centrifugation, and gravity sedimentation. Separate from the liquid after sulfidation. Examples of the sulfiding agent used in the sulfiding treatment include water-soluble sulfides such as hydrogen sulfide, alkali metal or alkaline earth metal sulfides, and hydrogen sulfide salts. Sodium hydrogen sulfide or sodium hydrosulfide is preferably used from the viewpoint of cost and ease of handling.

  The concentration of sulfide generated during sulfidation can be controlled by using a change in redox potential (ORP) accompanying the addition of a sulfiding agent as an index. In general, the higher the acid concentration, the easier the reaction proceeds, and even if the redox potential of the solution is sufficiently high, a precipitate is formed. As described above, the sulfuric acid concentration is generally 0.5 mol / l or more and 2.0 mol / l or less. In the above range, for example, by maintaining the silver-silver chloride electrode as a reference electrode in a range of 0 mV to 50 mV, rhenium can be favorably separated from the solution as rhenium sulfide precipitates. If the oxidation-reduction potential is lowered too much, an excessive amount of sulfiding agent is required, which is not preferable in terms of cost and working environment, and generally maintained at about 48 to 50 mV at a potential using a silver-silver chloride electrode as a reference electrode. It is appropriate to do.

[Example 1]
Each was added as a sulfate to have a copper concentration of 36.2 g / l, a zinc concentration of 0.52 g / l, an arsenic concentration of 5.72 g / l, and a cadmium concentration of 2.64 g / l, and a rhenium concentration of 0.75 g. An aqueous solution prepared to be / l was prepared. In this aqueous solution, the molar ratio ((Cu + Zn + Cd) / As) of the total content of copper, zinc, and cadmium to the content of arsenic is about 8. Such an aqueous solution (perrhenic acid-containing solution) was used as the original solution.

  To 1 liter of the original solution, an aqueous solution of sodium hydroxide having a concentration of 8 mol / l was added while stirring at room temperature, and the pH was adjusted to maintain the pH at 9. After the pH was stabilized, it was filtered using a filter paper and Nutsche, and separated into a filtrate and a precipitate. The obtained precipitate was washed with twice the amount of filtrate and collected separately from the filtrate.

  Precipitation ratios before and after pH adjustment of each component were calculated from the analytical values of these precipitates, filtrate and washing solution, and the respective quantities. The calculated results are shown in Table 1 below.

  As shown in Table 1, the precipitation rates of copper, zinc and cadmium all exceeded 99%, and the precipitation rate of arsenic was 99%. On the other hand, the precipitation rate of rhenium was only 3.9%, and it was found that copper, zinc, cadmium and arsenic can be selectively precipitated and separated from rhenium.

  Next, sulfuric acid with a concentration of 70% by weight was added to the filtrate obtained by the above filtration to adjust the sulfuric acid concentration to 1.4 mol / l (equivalent concentration 2.8 N). Further, an aqueous solution of sodium hydrogen sulfide having a concentration of 10% by weight is added to the adjustment solution after the addition of sulfuric acid, and the oxidation-reduction potential is adjusted to a range of 42 to 50 mV as measured using a silver-silver chloride electrode. Processed. The sulfidized adjustment liquid was filtered using a filter paper and Nutsche, and separated into a sulfided product and a sulfidized solution.

  Analysis of these post-sulfurized solution and sulfide sulfide confirmed that 99% of the rhenium contained in the filtrate after pH adjustment was recovered as sulfide precipitate. This means that 95% of the rhenium contained in the above original solution could be recovered as sulfide deposits.

[Example 2]
In the same manner as in Example 1 above, adjustment liquids of Samples 1 to 5 were prepared by changing the addition amount of sulfuric acid having a concentration of 70% by weight with respect to the filtrate obtained by pH adjustment and filtration. To these adjustment solutions, the same sodium hydrogen sulfide as in Example 1 was added while maintaining the oxidation-reduction potential during sulfidization at 50 mV with a silver-silver chloride electrode reference electrode. Further, as Samples 6 and 7, preparation solutions of sulfuric acid concentrations of 0.83 and 1.42 mol / l were prepared in the same manner as Samples 3 and 5, respectively, and sodium hydrogen sulfide was added to these Samples 6 and 7 in a large excess. Then, a treatment for reducing the oxidation-reduction potential to 45 mV or less was performed. Thereafter, in the same manner as in Example 1, after separation into a sulfided product and a solution after sulfidation, the precipitation rate of rhenium, that is, the recovery rate was measured. The measurement results are shown in Table 2 below.

  From the results in Table 2, it can be seen that when the oxidation-reduction potential (ORP) is 50 mV, the precipitation rate of rhenium increases as the sulfuric acid concentration increases. In particular, when the sulfuric acid concentration was 1.4 mol / l or more, a sufficient precipitation rate of 98% or more could be obtained. When an additional sulfurizing agent was added and the oxidation-reduction potential was lowered to 44 mV, the rhenium precipitation rate increased to 99% or more. Furthermore, when the sulfurizing agent was added excessively and lowered to 2 mV, a sufficient rhenium precipitation rate could be obtained even if the sulfuric acid concentration was 0.83 mol / l.

[Example 3]
Four types of the same original solution as in Example 1 were prepared for each liter, and the precipitate, filtrate and washing solution were the same as in Example 1 except that the pH values during pH adjustment were maintained at 7, 8, 10 and 11, respectively. Got. The rhenium and impurity precipitation rates in this case are shown in Table 3 below.

  As can be seen from Table 3, it was found that even when the pH value is 7 to 11, rhenium can be selectively separated as in Example 1. However, at pH 7, the cadmium precipitation rate decreased to 97%, and at pH 11, the arsenic precipitation rate decreased to 97%. From this result, it is possible to almost completely separate cadmium-containing impurities from rhenium by adjusting the pH to 8 or higher. When arsenic is contained in addition to cadmium, the rhenium is more selected by adjusting the pH to 8 to 10 It can be recovered.

1 1st process 2 2nd process 3 3rd process

Claims (4)

A method for separating rhenium from a solution containing one or more elements of copper, zinc, cadmium, and arsenic and perrhenic acid,
A first step of adding an alkali to the solution to form a precipitate, and solid-liquid separating the solution containing the precipitate;
A second step of adding an acid to the separation liquid obtained by the solid-liquid separation and adjusting the concentration of the acid within an equivalent concentration range of 1.0 N to 4.0 N;
A rhenium separation method comprising: a third step of adding a sulfiding agent to the adjustment liquid obtained by the addition of the acid to produce a sulfide precipitate, and separating the sulfide precipitate from the solution after sulfidation.   When arsenic coexists in the solution containing perrhenic acid, a compound containing at least one element of copper, zinc, and cadmium is added in advance to a concentration equal to or higher than the molar concentration of arsenic, The method for separating rhenium according to claim 1, wherein the first step to the third step are performed.   The method for separating rhenium according to claim 1 or 2, wherein, in the first step, the addition amount of the alkali is adjusted so that the pH of the solution is 8 or more.   In the third step, the addition amount of the sulfiding agent is adjusted so that the oxidation-reduction potential of the adjustment liquid is in the range of 0 mV to 50 mV in the measured value at the reference electrode of the silver-silver chloride electrode. The method for separating rhenium according to any one of claims 1 to 3.

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