WO2022113669A1 - Method for producing alkali metal salt of tungstic acid, method for producing tungsten, and composition containing alkali metal salt of tungstic acid - Google Patents

Method for producing alkali metal salt of tungstic acid, method for producing tungsten, and composition containing alkali metal salt of tungstic acid Download PDF

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WO2022113669A1
WO2022113669A1 PCT/JP2021/040440 JP2021040440W WO2022113669A1 WO 2022113669 A1 WO2022113669 A1 WO 2022113669A1 JP 2021040440 W JP2021040440 W JP 2021040440W WO 2022113669 A1 WO2022113669 A1 WO 2022113669A1
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alkali metal
tungsten
tungstic acid
metal salt
producing
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PCT/JP2021/040440
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French (fr)
Japanese (ja)
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幸司 安田
滉平 鈴木
理加 萩原
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国立大学法人京都大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B09B3/70—Chemical treatment, e.g. pH adjustment or oxidation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G41/00—Compounds of tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B34/00—Obtaining refractory metals
    • C22B34/30—Obtaining chromium, molybdenum or tungsten
    • C22B34/36—Obtaining tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
    • C22B5/14—Dry methods smelting of sulfides or formation of mattes by gases fluidised material

Definitions

  • the present invention relates to a method for producing an alkali metal salt of tungstic acid, a method for producing tungsten, and a composition containing an alkali metal salt of tungstic acid.
  • Tungsten is a metal with features such as high hardness, high heat resistance, high wear resistance, and high melting point, and is used in a wide range of industrial fields.
  • Cemented carbide tools which account for 80% of the domestic demand for tungsten, are typically made of a composite material in which 90 wt% tungsten carbide (WC) particles are bound with 8 wt% metallic cobalt. The remaining 2 wt% is an additive such as tantalum.
  • the molten nitrate method is known as one of the prior arts for recycling tungsten carbide.
  • scrap of a super hard tool is oxidatively dissolved by the oxidizing power of nitrate to obtain Na 2 WO 4 .
  • Further treatment of Na 2 WO 4 is obtained to obtain metallic tungsten (Patent Document 1).
  • the oxide is dissolved in the molten salt, so that the growth of the oxide on the surface of the WC does not stop and the treatment can be continuously proceeded.
  • the molten nitrate method has an advantage that hard scrap can be processed because the oxidative dissolution reaction proceeds at a high speed. On the other hand, it is difficult to treat powdered soft scrap having a large surface area by the molten nitrate method because of the possibility of explosion due to a huge exothermic reaction. In addition, since the reaction vessel is severely corroded, it is necessary to use an expensive material having corrosion resistance for the reaction vessel. Further, the molten nitrate method has a problem that toxic nitrogen oxides (NO x ) are generated as exhaust gas.
  • NO x toxic nitrogen oxides
  • Non-Patent Document 1 a method of using a molten carbonate instead of the molten nitrate has been proposed.
  • the molten carbonate method has advantages such as being able to process both hard scrap and soft scrap, no NO x being generated, and no possibility of explosion.
  • the aqueous solution becomes weakly alkaline in the dissolution treatment of the product in water, it is also an advantage that the separability between tungsten and other components is good.
  • the conventional molten carbonate method has a problem that the reaction rate of the oxidative dissolution reaction is not sufficient and the efficiency is poor. Possible causes are insufficient oxidizing power of the molten carbonate and low solubility of oxygen ion species (peroxide ion and superoxide ion) in the molten carbonate.
  • An object of the present invention is to provide a technique for recovering tungsten safely and efficiently.
  • the present invention Includes contacting a tungsten-containing material with a molten carbonate containing a metal ion that acts as an oxidant to the alkali metal carbonate and tungsten.
  • a method for producing an alkali metal salt of tungstic acid is provided.
  • the invention is: The method for producing an alkali metal salt of tungstic acid of the present invention is included. Provided is a method for producing tungsten.
  • the invention is: The method for producing an alkali metal salt of tungstic acid of the present invention is included. A method for producing ammonium paratungstate is provided.
  • the invention is: Alkali metal carbonate and Alkali metal salt of tungstic acid and Reduction products of metal ions that act as an oxidant for tungsten, Provided is a composition comprising an alkali metal salt of tungstic acid.
  • the invention is: Contains tungsten and cobalt, The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less.
  • alkali metal salts of tungstic acid are provided.
  • the invention is: Contains tungsten and cobalt, The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less. Provide ammonium paratungstate.
  • tungsten can be recovered safely and efficiently.
  • FIG. 1 is a process diagram of a method for recovering tungsten according to an embodiment of the present invention.
  • FIG. 2A is a schematic diagram of the process of step S1 of FIG.
  • FIG. 2B is a diagram showing a reaction in which an oxygen ion species oxidizes tungsten.
  • FIG. 2C is a diagram showing a reaction in which carbonate ions oxidize tungsten.
  • FIG. 3 is a schematic cross-sectional view of the reactor used in the examples.
  • FIG. 4 is an optical photograph of the cemented carbide chip of Example 1 after the reaction.
  • FIG. 5 shows the XRD pattern of the cemented carbide chip of Example 1 after the reaction.
  • FIG. 6A is an optical photograph of the cemented carbide chip of Example 3 after the reaction.
  • FIG. 6B is an optical photograph of the cemented carbide chip of Example 4 after the reaction.
  • FIG. 7A shows the XRD pattern of the carbide chip of Example 3 after the reaction.
  • FIG. 7B shows the XRD pattern of the carbide chip of Example 4 after the reaction.
  • FIG. 8 is an optical photograph of the crucibles of Examples 9, 10, 11 and 12 after the reaction.
  • FIG. 1 is a process diagram of a method for recovering tungsten according to an embodiment of the present invention.
  • the step of step S1 is a step of oxidizing and dissolving the tungsten-containing material in the molten carbonate.
  • the step of step S1 is a step of bringing the molten carbonate into contact with the tungsten-containing material.
  • the carbonate is an alkali metal carbonate.
  • FIG. 2A is a schematic diagram of the process of step S1 of FIG.
  • the necessary materials are put into the container 28.
  • the required materials are alkali metal carbonate, metal ion source and tungsten-containing material 24.
  • heating the container 28 with the heater 18 produces molten carbonate 22.
  • the molten carbonate 22 contains a metal ion derived from a metal ion source and an alkali metal carbonate.
  • the tungsten-containing material 24 is contained in the container 28 so that the tungsten-containing material 24 is in contact with the molten carbonate 22.
  • a metal ion source may be added to the container 28.
  • the tungsten-containing material 24 may be added to the container 28.
  • the tungsten contained in the tungsten-containing material 24 can be efficiently oxidized. Can be done.
  • the oxidized tungsten dissolves in the molten carbonate 22 in the form of tungstic acid ions.
  • the oxidative dissolution reaction proceeds rapidly, but is not explosive. Therefore, powdered tungsten-containing materials can also be processed. Since no toxic exhaust gas is generated, the equipment cost is low and the environment is not polluted. High corrosion resistance is not required for the container 28, and various materials can be used as the material for the container 28.
  • the alkali metal carbonate comprises at least one selected from the group consisting of Na 2 CO 3 , Li 2 CO 3 and K 2 CO 3 .
  • Na 2 CO 3 and K 2 CO 3 are recommended due to their low cost.
  • the melting point of Na 2 CO 3 is 851 ° C.
  • the eutectic point of the Na 2 CO 3 ⁇ Li 2 CO 3 system is 497 ° C.
  • the eutectic point of the Na 2 CO 3 -K 2 CO 3 system is 702 ° C.
  • the eutectic point of the K 2 CO 3 ⁇ Li 2 CO 3 system is 488 ° C.
  • the eutectic point of the Na 2 CO 3 -Li 2 CO 3 -K 2 CO 3 system is 390 ° C.
  • the melting point of the alkali metal carbonate is lowered, and tungsten can be recovered at a lower temperature, which is advantageous in terms of energy consumption.
  • Alkali metal carbonate may be used properly according to the type of the metal ion source.
  • the metal ion source supplies metal ions that act as an oxidizing agent to tungsten by dissolving in a melt of an alkali metal carbonate. Specifically, the metal ion source acts as an oxidant for the tungsten component contained in the tungsten-containing material 24.
  • the metal ion derived from the metal ion source includes not only the metal ion (cation) represented by M n + but also the metal oxo anion represented by MO a b- (a, b, n are positive integers). ).
  • the metals contained in the metal ion source are metals other than alkali metals, alkaline earth metals, lanthanides and actinides.
  • a metalloid such as Sb is also included in "metal".
  • the metal ion source can be a metal compound that does not generate NO x and can supply metal ions that act as an oxidizing agent for tungsten.
  • metal compounds include metal oxides, metal carbonates, metal sulfates and the like.
  • the metal compound preferably comprises at least one selected from the group consisting of metal oxides and metal carbonates.
  • the metal oxide is dissolved in the melt of the alkali metal carbonate according to the acidic dissolution of the following formula (1a) or the basic dissolution of (1b).
  • the metal ion derived from the metal oxide oxidizes the tungsten contained in the tungsten-containing material 24 according to the following formula (2a) or (2b).
  • the metal ion is reduced and changed to a reduction product 26 such as a simple substance metal.
  • the metal oxide dissolves in a melt of an alkali metal carbonate to generate metal ions and oxide ions. Both metal ions and oxide ions act as oxidants, and unnecessary ions are not generated in the molten carbonate.
  • Unwanted ions may reduce the solubility of oxides and alkali metal salts of tungstic acid in the molten carbonate 22.
  • a metal oxide may be produced by oxidizing the reduction product 26 (step S8 described later). The obtained metal oxide can be reused as an oxidizing agent.
  • the metal oxide may be a composite oxide. In the following equation, a, b, p, q, r and x each represent a positive integer.
  • Metallic carbonates such as CuCO 3 and FeCO 3 exist as compounds at room temperature. However, when it is dissolved in a high-temperature alkali metal carbonate melt, it is thermally decomposed according to the following formulas (3a) and (3b), for example.
  • the metal oxide is dissolved in the melt of the alkali metal carbonate according to the above formula (1a). CO 2 diffuses into the surrounding atmosphere as a gas. That is, when a metal carbonate is used, the same result as when a metal oxide is used can be obtained.
  • the metal ion M n + is completely reduced to zero valence.
  • the metal ion M n + may be reduced to M m + (n> m) having a smaller valence.
  • the metal ion derived from the metal oxide oxidizes the tungsten contained in the tungsten-containing material 24 according to the following formula (2c) or (2d).
  • a, b, c, d, p, q, m and n each represent a positive integer.
  • FIG. 2A shows the oxidation-dissolution reaction of tungsten. Even when a tungsten compound such as tungsten carbide is used, tungsten is oxidized by a reaction according to the above formulas (2a) to (2d) and dissolved in the molten carbonate 22.
  • the metal ion to be supplied from the metal ion source contains at least one selected from the group consisting of Cu ion, Fe ion, Ni ion, Sn ion, Mn ion, V ion, Pb ion, Sb ion, and Co ion. You may be. These metal ions can oxidize tungsten.
  • the metal ions to be supplied from the metal ion source are Cu (+1), Cu (+2), Fe (+2), Fe (+3), Ni (+2), Sn (+2), Sn (+4), Mn (+2). ), Mn (+4), V (+2), V (+3), V (+4), V (+5), Pb (+2), Pb (+4), Sb (+3), Sb (+4), Sb (+5) ), Co (+2), and Co (+3) may contain at least one selected from the group. These metal ions can oxidize tungsten.
  • the metal ion is used in this embodiment. It is possible. According to this embodiment, since the redox potential of the molten carbonate 22 can be controlled by the type of metal ion, it is easy to treat a powdered tungsten-containing material having a large surface area.
  • the redox potential of the molten nitrate is defined by NO x generated in the reaction, so that it is practically impossible to control the redox potential of the molten nitrate.
  • the metal oxides that can supply the above-mentioned metal ions are CuO, Cu 2 O, FeO, Fe 2 O 3 , NiO, SnO, SnO 2 , MnO, MnO 2 , VO, V 2 O 3 , VO 2 , respectively.
  • the metal oxide may contain at least one selected from the group consisting of CuO, Cu2O , VO, V2O3 , VO2 , and V2O5 .
  • the solubility of copper oxide in the molten carbonate 22 is high. Therefore, when copper oxide is used as the metal oxide, copper ions and oxide ions can be reliably generated. Further, when the metal contained in the metal oxide does not form an alloy with the metal contained in the tungsten-containing material 24, the separation of each metal is easy in the downstream process. For example, scrap of cemented carbide tools contains a large amount of Co. Since Cu and Co do not form an alloy, Cu and Co can be sorted by a known method such as magnetic force sorting. Therefore, it is recommended to use CuO and / or Cu 2O as the metal oxide when processing the scrap of the cemented carbide tool by the method of this embodiment. Vanadium oxide is also recommended because it has a strong ability to oxidize tungsten.
  • the amount of alkali metal carbonate used to prepare the molten carbonate 22 is, for example, 0.3 mol or more and 20 mol or less with respect to 1 mol of tungsten contained in the tungsten-containing material to be treated. This makes it possible to sufficiently oxidize and dissolve tungsten. For example, a maximum of 3.3 mol of Na 2 WO 4 is dissolved in 1 mol of Na 2 CO 3 . From this point of view, the lower limit of the amount of alkali metal carbonate is determined. The upper limit of the amount of alkali metal carbonate is determined from the viewpoint of economy.
  • the amount of the metal ion source added to the molten carbonate 22 is not particularly limited.
  • the amount of alkali metal carbonate used is used as a reference (100 mol%), the amount of the metal ion source added is, for example, 0.5 mol% or more and 50 mol% or less.
  • the oxidizing power derived from the alkali metal carbonate is exerted by peroxide ions (O 2 2- ), superoxide ions (O 2- ) and carbonate ions (CO 3 2- ).
  • FIG. 2B is a diagram showing a reaction in which oxygen ion species (O 2 2- , O 2- ) oxidize tungsten.
  • FIG. 2C is a diagram showing a reaction in which carbonate ions (CO 3 2- ) oxidize tungsten.
  • O 2 in the atmosphere is chemically dissolved in the molten carbonate as O 2 2- ion or O 2 - ion, diffused in the molten carbonate, and then tungsten is formed. Oxidize.
  • CO 3 2- present in the molten carbonate directly oxidizes tungsten.
  • the target temperature of the molten carbonate 22 is determined according to the melting point of the alkali metal carbonate.
  • the target temperature of the molten carbonate 22 is, for example, 500 ° C. or higher and 1000 ° C. or lower.
  • the target temperature may be 700 ° C. or higher and 950 ° C. or lower.
  • the target temperature of the molten carbonate 22 may be set in consideration of the solubility of the metal ion source in the molten carbonate 22. This is because when the metal ion source is sufficiently dissolved in the molten carbonate 22, the metal ions acting as an oxidizing agent are sufficiently supplied from the metal ion source.
  • the predetermined time for maintaining the molten carbonate 22 at the target temperature is not particularly limited, and is, for example, 0 hours or more and 50 hours or less, preferably 25 hours or less, more preferably 5 hours or less, still more preferably 2.5 hours. It's less than an hour. According to this embodiment, the reaction can be sufficiently advanced in a short time. “0 hours” means that the temperature of the molten carbonate 22 is raised at a predetermined rate, and after the molten carbonate 22 reaches the target temperature, the temperature lowering process is immediately started. As will be clear from the examples described later, the reaction can proceed even in this case. After maintaining the molten carbonate 22 at the target temperature for a predetermined time, the temperature of the molten carbonate 22 may be lowered to room temperature at a predetermined rate.
  • scrap of a cemented carbide tool containing tungsten carbide as a main component can be mentioned.
  • the scrap of the cemented carbide tool may be a large hard scrap that retains the shape of the cemented carbide tool, may be a powdery soft scrap, or may contain both of them. According to the method of the present embodiment, both hard scrap and soft scrap can be safely processed.
  • "Main component" means the component contained most in the mass ratio.
  • the material of the container 28 is not particularly limited, and may be, for example, a ceramic such as alumina, or a metal material such as iron or nickel.
  • the molten nitrate method described in Patent Document 1 requires an expensive container having corrosion resistance. However, according to the present embodiment, there is no such restriction, and various materials can be used as the material of the container 28.
  • the surrounding atmosphere in which the container 28 is placed is not particularly limited.
  • the ambient atmosphere may be an inert atmosphere or an oxidizing atmosphere.
  • An inert gas such as a noble gas or N 2 gas is used for the inert atmosphere.
  • the oxidizing atmosphere include an atmosphere containing an oxidizing agent gas such as O 2 gas.
  • a mixed gas of the inert gas and the oxidant gas may be used as the atmospheric gas. The partial pressure of each component in the mixed gas is adjusted appropriately.
  • the pressure of the ambient atmosphere is not particularly limited and may be substantially equal to the atmospheric pressure.
  • the atmospheric gas with which the molten carbonate 22 is in contact may contain CO 2 gas.
  • a mixed gas of a noble gas and a CO 2 gas can be used as the atmospheric gas.
  • the partial pressure of each gas is not particularly limited.
  • the partial pressure of the CO 2 gas is, for example, 1 ⁇ 10 -7 atm or more and 1 atm or less, preferably 1 ⁇ 10 -4 atm or more and 0.8 atm or less.
  • the lower limit of the partial pressure of CO 2 gas is determined based on the value assumed when the atmosphere is diluted with another gas.
  • the lower limit of the partial pressure of CO 2 gas is determined based on the value assumed when another gas such as O 2 gas is added to pure CO 2 gas.
  • the partial pressure of the CO 2 gas By adjusting the partial pressure of the CO 2 gas, it is possible to control the basicity of the molten carbonate 22. Thereby, the reaction rate of the oxidative dissolution reaction can be controlled.
  • the partial pressure of the CO 2 gas By adjusting the partial pressure of the CO 2 gas, it is also possible to adjust the solubility of the metal ion source in the molten carbonate 22 and the solubility of the alkali metal salt of tungsten acid in the molten carbonate 22.
  • the partial pressure of the CO 2 gas may be adjusted according to the type of metal ion.
  • the basicity of the molten nitrate is defined by NO x generated in the reaction, so that it is practically impossible to control the basicity of the molten nitrate.
  • the molten carbonate 22 may be stirred in the step S1.
  • Metals derived from metal ion sources are deposited on the surface of the carbide tool tip. By stirring, the metal deposited from the surface of the chip can be removed. As a result, the oxidation-dissolution reaction of tungsten can proceed more smoothly.
  • O 2 gas may be bubbled to the molten carbonate 22.
  • oxygen ion species O 2 2- , O 2-
  • metal ions as an oxidizing agent can be regenerated by the O 2 gas reoxidizing the metal after oxidizing tungsten.
  • the composition comprises an alkali metal salt of tungsten acid, an unreacted alkali metal carbonate, and a reduction product 26 of the metal ion derived from the metal ion source.
  • the reduction product 26 typically contains a simple metal, may contain a salt such as NaVO 2 , or may contain both.
  • the composition may further contain an unreacted tungsten-containing material 24 and by-products. By-products include metal residues, alkali metal oxides and the like. The metal residue contains other metals contained in the tungsten-containing material and the like.
  • other metals include Co and Ta.
  • the composition containing the alkali metal salt of tungstic acid is, for example, in the form of powder.
  • the presence of the alkali metal carbonate and the alkali metal salt of tungsten acid can be confirmed.
  • the presence of elemental metals derived from metal ion sources can be confirmed by inductively coupled plasma emission spectroscopy.
  • an aqueous solution of the alkali metal salt of tungsten acid can be easily obtained only by adding water to the composition containing the alkali metal salt of tungsten acid.
  • the composition containing the alkali metal salt of tungstic acid is excellent in storage and transportability. Therefore, the composition may be transported to another location to carry out the downstream process.
  • step S2 of FIG. 1 water is added to the container 28, and the composition containing the alkali metal salt of tungstic acid is dissolved in water.
  • Substances that are insoluble in water precipitate as solids.
  • the pH of the aqueous solution may be appropriately adjusted.
  • Alkali metal salts of tungstic acid are neutral or alkaline and are well soluble in water.
  • the aqueous solution containing the alkali metal salt of tungstic acid is weakly acidic.
  • a weakly alkaline aqueous solution can be obtained. Therefore, it is possible to obtain a tungsten aqueous solution having a low solubility of components other than tungsten and a lower impurity concentration.
  • the ratio (M2 / M1) of the cobalt concentration M2 (unit: mass ppm) to the tungsten concentration M1 (unit: mass ppm) is a percentage. In representative, it is preferably 0.5% or less, and more preferably 0.25% or less.
  • the lower limit of the ratio (M2 / M1) is not particularly limited, and is, for example, 0.0001%, which may be equal to or lower than the lower limit of detection.
  • step S3 of FIG. 1 solid-liquid separation of an aqueous solution containing an alkali metal salt of tungstic acid is performed.
  • a water-insoluble precipitate eg, Cu, Co, Ta, etc.
  • the method of solid-liquid separation is not particularly limited, and known methods such as filtration, centrifugation, and precipitation can be adopted.
  • step S8 the metal used in step S1 is recovered from the precipitate recovered in step S3.
  • the recovered metal is oxidized to obtain a metal oxide.
  • the obtained metal oxide can be reused in the step S1 and is economical.
  • an aqueous solution containing an alkali metal salt of tungsten acid is treated by ion exchange using an ion exchange resin.
  • the alkali metal ion is replaced with ammonium ion, and an aqueous solution of ammonium tungstate ((NH 4 ) 2 WO 4 ) is obtained.
  • the ammonium paratungate aqueous solution is concentrated to crystallize ammonium paratungate (APT: Ammonium paratungstate).
  • APT Ammonium paratungstate
  • the ratio (m2 / m1) of the cobalt concentration m2 (unit: mass ppm) to the tungsten concentration m1 (unit: mass ppm) is preferably 0.5% or less in terms of percentage, and more. It is preferably 0.25% or less.
  • the lower limit of the ratio (m2 / m1) is not particularly limited, and is, for example, 0.0001%, which may be equal to or lower than the detection lower limit.
  • step S6 of FIG. 1 ammonium paratungstate is dried and roasted. This gives tungsten oxide (WO 3 ).
  • step S7 of FIG. 1 the tungsten oxide is reduced.
  • metallic tungsten (W) is obtained.
  • the reduction of tungsten oxide is carried out by a known method such as hydrogen reduction.
  • the following experiment was conducted to confirm whether the metal oxide functions as an oxidizing agent in the process of recovering tungsten as an alkali metal salt of tungsten acid from the super hard chip by the molten carbonate method.
  • FIG. 3 is a schematic cross-sectional view of the reactor used in the examples.
  • the reaction apparatus 10 includes a reaction tube 11 made of alumina, a stainless steel lid 12, and an electric furnace 17.
  • the reaction tube 11 is closed by the stainless steel lid 12.
  • the reaction tube 11 is housed in an electric furnace 17.
  • the stainless steel lid 12 is provided with an inlet port 13 and an outlet port 14.
  • a supply pipe 15 is attached to the inlet port 13.
  • An exhaust pipe 16 is attached to the outlet port 14.
  • the atmosphere inside the reaction tube 11 can be adjusted through the supply pipe 15 and the exhaust pipe 16.
  • a crucible 20 is arranged inside the reaction tube 11.
  • the molten carbonate 22 and the tungsten-containing material 24 are arranged in the crucible 20. By heating the reaction tube 11, molten carbonate 22 is generated from the raw material, and the reaction proceeds.
  • Example 1 As raw materials for molten carbonate, Na 2 CO 3 powder (manufactured by Fujifilm Wako Junyaku Co., Ltd.) crushed by a mortar and pestle and a metal oxide used as an oxidant are used in an alumina crucible (manufactured by Nikkato Corporation, SSA). -S, outer diameter 37 mm x height 25 mm) was filled. The amount of Na 2 CO 3 was 3.1 g, and the depth of the molten salt at the time of dissolution was adjusted to 6 mm. Cu 2 O (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide. Based on the amount of Na 2 CO 3 used (100 mol%), the amount of Cu 2 O added was 6.4 mol%. The crucible filled with Na 2 CO 3 powder and metal oxide was dried overnight in a vacuum oven at 180 ° C. to remove residual water.
  • a cemented carbide chip (TPG070202FN, 450 mg, manufactured by Daishowa Seiki Co., Ltd.) was embedded in Na 2 CO 3 powder in a crucible and allowed to stand. Then, as described with reference to FIG. 3, a crucible was placed in an airtight container having a reaction tube (outer diameter 80 mm ⁇ inner diameter 70 mm ⁇ length 500 mm) and a stainless steel lid and allowed to stand. A supply pipe and an exhaust pipe were fixed to each port of the stainless steel lid by an O-ring. The stainless steel lid was air-cooled with a cooling fan to prevent deterioration of the O-ring.
  • reaction tube After inserting the reaction tube into a horizontal electric furnace (KTF040N1 manufactured by Koyo Thermo System Co., Ltd.), the temperature was raised from room temperature at 5 ° C./min, and after reaching 900 ° C., the reaction was allowed to proceed for 25 hours.
  • Alumina protection pipes manufactured by Nikkato Corporation, SSA-S, outer diameter 6.0 mm x inner diameter 4.0 mm) were used as the supply pipe and the exhaust pipe.
  • the obtained salt was dissolved in nitrate containing tartrate acid, which is a chelating agent for tungsten ions, and then the tungsten concentration was analyzed by inductively coupled plasma emission spectroscopy (ICP-AES, AMETEK, SPECTROBLUE). From this, it was confirmed that the weight loss rate was the oxidative elution of tungsten carbide in the cemented carbide chip.
  • An X-ray diffractometer (XRD, manufactured by Rigaku, SmartLab, Cu-K ⁇ ray, 40 kV, 30 mA) was used to identify the phase of the obtained salt and the residual cemented carbide chip.
  • Example 1 to which Cu 2 O was added showed a larger weight loss rate than Comparative Example 1.
  • the reason for this is that Cu 2 O functions as an oxidant and the oxidative elution reaction of tungsten proceeds rapidly.
  • FIG. 4 is an optical photograph of the cemented carbide chip of Example 1 after the reaction. As shown in the left figure of FIG. 4, orange-red precipitates were deposited on the surface of the cemented carbide chip. As shown in the right figure of FIG. 4, when the surface precipitate was peeled off, a black unreacted chip remained inside.
  • FIG. 5 shows the XRD pattern of the cemented carbide chip of Example 1 after the reaction.
  • the XRD pattern of Cu powder and the XRD pattern of Co powder are also shown. From the comparison with the XRD pattern of Cu powder and the XRD pattern of Co powder, it was confirmed that the precipitate was metallic Cu.
  • the small peak of the metal Co is a peak derived from the metal Co adhering to Cu.
  • Example 2 The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 3.
  • Example 2 Even if the partial pressure of CO 2 was lowered, Example 2 showed a large weight loss rate due to the addition of Cu 2 O. However, Example 1 having a high CO 2 partial pressure showed a larger weight loss rate than Example 2 having a low CO 2 partial pressure.
  • Example 3 The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that 6.4 mol% FeO (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 4.
  • Example 4 Except for the fact that 2.1 mol% Fe 2 O 3 (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide, the oxidative dissolution treatment of the superhard chip by the molten carbonate method was carried out in the same manner as in Example 1. did. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 4.
  • Example 3 to which FeO was added and Example 4 to which Fe 2O 3 was added showed a larger weight loss rate than that of Comparative Example 1.
  • the reason for this is that FeO and Fe 2 O 3 function as oxidizing agents, and the oxidative elution reaction proceeds rapidly.
  • Example 3 when the oxidative elution reaction is represented by the following formula (A2), 6.4 mol% of FeO corresponds to 20.1% in terms of the weight loss rate of tungsten carbide.
  • Example 4 when the oxidation elution reaction is represented by the following formula (A3), 2.1 mol% of Fe 2 O 3 corresponds to 20.1% in terms of the weight loss rate of tungsten carbide.
  • FIG. 6A is an optical photograph of the cemented carbide chip of Example 3 after the reaction.
  • FIG. 6B is an optical photograph of the cemented carbide chip of Example 4 after the reaction. Silver-colored precipitates having a metallic luster were deposited on the surfaces of the cemented carbide chips of Examples 3 and 4, respectively.
  • FIG. 7A shows the XRD pattern of the cemented carbide chip of Example 3 after the reaction.
  • FIG. 7B shows the XRD pattern of the carbide chip of Example 4 after the reaction.
  • Each XRD pattern showed a peak of Fe. From this, it was confirmed that the surface precipitates in Examples 3 and 4 were metallic Fe.
  • Example 5 The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 3 except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 3. The results are shown in Table 5.
  • Example 6 The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 4 except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 4. The results are shown in Table 5.
  • Examples 5 and 6 showed a slightly larger weight loss rate than Comparative Example 2. On the other hand, Examples 5 and 6 showed a smaller weight loss rate than Examples 3 and 4. The reason for this is that FeO and Fe 2 O 3 have low solubility in carbonate at low CO 2 partial pressure. Therefore, when FeO and Fe 2 O 3 are used, the control of the partial pressure of CO 2 is more important for promoting the oxidative dissolution reaction.
  • Example 7 Except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm and the reaction time was changed to 2.5 hours, the super hard chip by the molten carbonate method was used in the same manner as in Example 1. An oxidative dissolution treatment was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
  • Example 8 Examples except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm, the amount of Cu 2 O added was changed to 12.8 mol%, and the reaction time was changed to 0 hour.
  • the oxidative dissolution treatment of the super hard chip by the molten carbonate method was carried out by the same method as in 1. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
  • the reaction time of 0 hours means that the temperature of the molten carbonate is raised to 900 ° C. and then immediately lowered.
  • Example 9 Except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm, the amount of Cu 2 O added was changed to 12.8 mol%, and the reaction time was changed to 2.5 hours.
  • the oxidative dissolution treatment of the super hard chip by the molten carbon dioxide method was carried out by the same method as in Example 1. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
  • the measured values of inductively coupled plasma emission spectroscopy for the salt obtained in Example 9 were 40.7 mass ppm for tungsten and 0.01 mass ppm or less, which is the detection limit for cobalt. Therefore, the ratio of the cobalt concentration to the tungsten concentration in the alkali metal salt was 0.5% or less (0.25% or less). Further, since the tungsten concentration does not change at least in ion exchange, it can be easily inferred that the ratio of the cobalt concentration to the tungsten concentration in ammonium paratungstate is 0.5% or less (0.25% or less). Cobalt is derived from the binder contained in the carbide chip and is an impurity contained in the alkali metal salt of tungstic acid and ammonium paratungstate.
  • Example 3 Melting by the same method as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm, Cu 2 O was not added, and the reaction time was changed to 0 hours. The oxidative dissolution treatment of the super hard chip by the carbonate method was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
  • Example 4 The same method as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 ⁇ 10 -4 atm, Cu 2 O was not added, and the reaction time was changed to 2.5 hours. The oxidative dissolution treatment of the super hard chip was carried out by the molten carbon dioxide method. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
  • Example 7 The weight loss rate in Example 7 was almost equal to the weight loss rate in Example 2 (Table 3). This indicates that the oxidative dissolution reaction was almost completed in 2.5 hours.
  • Example 8 with a reaction time of 0 hours also showed a weight loss rate of 8.3%. This indicates that the oxidative dissolution reaction proceeded even in the process of raising and lowering the temperature.
  • Example 10 The CO 2 partial pressure was changed to 6.0 ⁇ 10 -4 atm, and tungsten carbide powder (manufactured by High Purity Chemical Co., Ltd., average particle size 150 ⁇ m, 100 mg) was used instead of the super hard chip. Tungsten carbide powder was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that the addition amount was changed to 12.8 mol% and the reaction time was changed to 2.5 hours. .. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 7.
  • Example 10 is much larger than the weight loss rate in Comparative Example 4 (Table 6), and the weight loss rate in Example 9 (Table 6) under the same conditions except that the tungsten carbide is a powder is the same. Was bigger than.
  • Example 11 K 2 CO 3 powder was used as a carbonate instead of Na 2 CO 3 powder, the CO 2 partial pressure was changed to 6.0 ⁇ 10 -4 atm, and the amount of Cu 2 O added was 12.8 mol%.
  • the oxidative dissolution treatment of the super hard chip by the molten carbonate method was carried out by the same method as in Example 1 except that the reaction time was changed to 2.5 hours. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 8.
  • Example 11 12.8 mol% of Cu 2 O corresponds to 40.2% in terms of the weight loss rate of tungsten carbide.
  • the weight loss rate in Example 11 was about the same as the weight loss rate in Example 9 (Table 6). As can be understood from the results of Example 11, the oxidative dissolution reaction proceeded sufficiently even when K 2 CO 3 was used as the carbonate.
  • Example 12 A mixture of Na 2 CO 3 powder and K 2 CO 3 powder was used as a carbonate, the CO 2 partial pressure was changed to 6.0 ⁇ 10 -4 atm, and the amount of Cu 2 O added was 12.8 mol.
  • 12.8 mol% of Cu 2 O corresponds to 40.2% in terms of the weight loss rate of tungsten carbide.
  • the weight loss rate in Example 12 was lower than that of Example 9 (Table 6) using molten Na 2 CO 3 at 900 ° C., and from Example 11 (Table 8) using molten K 2 CO 3 at 900 ° C. Was also low. This is considered to be related to the eutectic temperature of the Na 2 O-Cu 2 O system being 806 ° C. That is, it is expected that the weight loss rate in Example 12 was low because the solubility of Cu 2 O in the molten salt was high at 900 ° C., but the solubility of Cu 2 O in the molten salt was low at 780 ° C. From this result, when Cu 2 O or Cu O is used, it is desirable to set the target temperature of the molten salt in the range of 800 ° C. or higher and 1000 ° C. or lower.
  • FIG. 8 is an optical photograph of the crucibles of Examples 9, 10, 11 and 12 after the reaction.
  • FIGS. 8 (a) and 8 (b) show the results in Examples 9 and 10, respectively, which contain only Na 2 CO 3 as a carbonate.
  • FIG. 8 (c) shows the results in Example 11 containing only K 2 CO 3 as a carbonate.
  • FIG. 8 (d) shows the results in Example 12 containing both Na 2 CO 3 and K 2 CO 3 as carbonates.
  • Example 9 in Example 9 using only Na 2 CO 3 , metal Cu (dark colored portion) is intensively adhered to the surface of the cemented carbide chip.
  • metal Cu (dark colored portion) was deposited on the bottom of the crucible.
  • FIGS. 8 (c) and 8 (d) in Examples 11 and 12 using K 2 CO 3 , the product (mainly the alkali metal salt of tungstic acid) was entirely covered with metallic Cu (dense). The colored part) was dispersed. The cause is expected to be the difference in wettability and surface tension of metallic Cu. Cu adhering to the surface of the cemented carbide chip may inhibit the diffusion of ions and delay the oxidative dissolution reaction. The use of K 2 CO 3 as the carbonate may avoid such disadvantages.
  • Example 13 to 16 Oxidation-dissolution treatment of cemented carbide chips by the molten carbonate method in the same manner as in Example 9 except that 12.8 mol% MnO 2 , SnO 2 , Sb 2 O 3 or V 2 O 5 was used as the metal oxide. Was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 10.
  • 12.8 mol% of MnO 2 , SnO 2 , Sb 2 O 3 , and V 2 O 5 are 80.4%, 80.4%, and 120.6%, respectively, when converted to the weight loss rate of tungsten carbide. And 201%.
  • Example 16 The weight loss rate of Examples 13 to 16 was larger than the weight loss rate (2.0%) of Comparative Example 4 (Table 6) under the same experimental conditions except that no metal oxide was added. In Example 16 using V 2 O 5 , the weight could not be measured because the carbide chips were completely changed to powder. In Example 16, when the tungsten concentration in the recovered salt was measured by ICP-AES, 62.2% of the tungsten in the cemented carbide chip was dissolved. In other words, vanadium oxide exerted a very high effect.
  • Example 17 Except for the fact that Co 3 O 4 or Ni O was used as the metal oxide, the cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 7. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 11.
  • the present invention is useful for recovering tungsten from a tungsten-containing material.

Abstract

A method for producing an alkali metal salt of tungstic acid according to the present invention comprises a process wherein a molten carbonate, which contains metal ions that serve as an oxidant with respect to an alkali metal carbonate and tungsten, and a tungsten-containing material are brought into contact with each other. The metal ions are supplied, for example, from at least one substance that is selected from the group consisting of metal oxides and metal carbonates. The metal ions may include at least one kind of ions that are selected from the group consisting of Cu ions, Fe ions, Ni ions, Sn ions, Mn ions, V ions, Pb ions, Sb ions and Co ions.

Description

タングステン酸のアルカリ金属塩の製造方法、タングステンの製造方法及びタングステン酸のアルカリ金属塩を含む組成物A method for producing an alkali metal salt of tungstic acid, a method for producing tungsten, and a composition containing an alkali metal salt of tungstic acid.
　本発明は、タングステン酸のアルカリ金属塩の製造方法、タングステンの製造方法及びタングステン酸のアルカリ金属塩を含む組成物に関する。 The present invention relates to a method for producing an alkali metal salt of tungstic acid, a method for producing tungsten, and a composition containing an alkali metal salt of tungstic acid.
　タングステンは、高硬度、高耐熱性、高耐摩耗性、高融点などの特徴を有する金属であり、幅広い産業分野において利用されている。タングステンの国内需要の８０％を占める超硬工具は、代表的な組成として９０ｗｔ％の炭化タングステン（ＷＣ）粒子を８ｗｔ％の金属コバルトで結着した複合材料でできている。残りの２ｗｔ％は、タンタルなどの添加材である。超硬工具のスクラップには、超硬工具の形状を保った大きいハードスクラップと、粉末状のソフトスクラップとの２種類がある。 Tungsten is a metal with features such as high hardness, high heat resistance, high wear resistance, and high melting point, and is used in a wide range of industrial fields. Cemented carbide tools, which account for 80% of the domestic demand for tungsten, are typically made of a composite material in which 90 wt% tungsten carbide (WC) particles are bound with 8 wt% metallic cobalt. The remaining 2 wt% is an additive such as tantalum. There are two types of scrap for cemented carbide tools: large hard scrap that retains the shape of the cemented carbide tool and powdered soft scrap.
　炭化タングステンをリサイクルするための従来技術の１つとして、溶融硝酸塩法が知られている。溶融硝酸塩法では、超硬工具のスクラップを硝酸塩の酸化力により酸化溶解させてＮａ2ＷＯ4を得る。Ｎａ2ＷＯ4を更に処理して金属タングステンを得る（特許文献１）。溶融硝酸塩法によれば、酸化物が溶融塩へと溶解することで、ＷＣ表面の酸化物の成長が停止せず、連続的に処理を進めることが可能である。 The molten nitrate method is known as one of the prior arts for recycling tungsten carbide. In the molten nitrate method, scrap of a super hard tool is oxidatively dissolved by the oxidizing power of nitrate to obtain Na 2 WO 4 . Further treatment of Na 2 WO 4 is obtained to obtain metallic tungsten (Patent Document 1). According to the molten nitrate method, the oxide is dissolved in the molten salt, so that the growth of the oxide on the surface of the WC does not stop and the treatment can be continuously proceeded.
国際公開第２０１０／１０４００９号International Publication No. 2010/10409
　溶融硝酸塩法は、酸化溶解反応が高速で進むためハードスクラップも処理できるという利点を有する。一方、巨大な発熱反応で爆発の可能性もあるため、表面積が大きい粉末状のソフトスクラップを溶融硝酸塩法で処理することは困難である。また、反応容器の腐食も激しいため、耐食性を有する高価な材料を反応容器に使用する必要がある。さらに、溶融硝酸塩法には、有毒な窒素酸化物（ＮＯx）が排気ガスとして発生するという問題もある。 The molten nitrate method has an advantage that hard scrap can be processed because the oxidative dissolution reaction proceeds at a high speed. On the other hand, it is difficult to treat powdered soft scrap having a large surface area by the molten nitrate method because of the possibility of explosion due to a huge exothermic reaction. In addition, since the reaction vessel is severely corroded, it is necessary to use an expensive material having corrosion resistance for the reaction vessel. Further, the molten nitrate method has a problem that toxic nitrogen oxides (NO x ) are generated as exhaust gas.
　そこで、溶融硝酸塩に代えて、溶融炭酸塩を用いる方法が提案されている（非特許文献１）。溶融炭酸塩法は、ハードスクラップ及びソフトスクラップの両方を処理できる、ＮＯxが発生しない、爆発の可能性が無いといった利点を有する。また、生成物の水への溶解処理では、水溶液が弱アルカリ性となるため、タングステンとその他の成分との分離性が良い点も利点である。一方、従来の溶融炭酸塩法には、酸化溶解反応の反応速度が十分でなく、効率が悪いという問題があった。原因としては、溶融炭酸塩の酸化力の不足、及び、溶融炭酸塩への酸素イオン種（過酸化物イオン及び超酸化物イオン）の溶解度が低いことが考えられる。 Therefore, a method of using a molten carbonate instead of the molten nitrate has been proposed (Non-Patent Document 1). The molten carbonate method has advantages such as being able to process both hard scrap and soft scrap, no NO x being generated, and no possibility of explosion. In addition, since the aqueous solution becomes weakly alkaline in the dissolution treatment of the product in water, it is also an advantage that the separability between tungsten and other components is good. On the other hand, the conventional molten carbonate method has a problem that the reaction rate of the oxidative dissolution reaction is not sufficient and the efficiency is poor. Possible causes are insufficient oxidizing power of the molten carbonate and low solubility of oxygen ion species (peroxide ion and superoxide ion) in the molten carbonate.
　本発明の目的は、安全かつ効率的にタングステンを回収する技術を提供することにある。 An object of the present invention is to provide a technique for recovering tungsten safely and efficiently.
　本発明は、
　アルカリ金属炭酸塩及びタングステンに対して酸化剤として働く金属イオンを含有する溶融炭酸塩とタングステン含有材料とを接触させることを含む、
　タングステン酸のアルカリ金属塩の製造方法を提供する。 The present invention
Includes contacting a tungsten-containing material with a molten carbonate containing a metal ion that acts as an oxidant to the alkali metal carbonate and tungsten.
Provided is a method for producing an alkali metal salt of tungstic acid.
　別の側面において、本発明は、
　上記本発明のタングステン酸のアルカリ金属塩の製造方法を含む、
　タングステンの製造方法を提供する。 In another aspect, the invention is:
The method for producing an alkali metal salt of tungstic acid of the present invention is included.
Provided is a method for producing tungsten.
　さらに別の側面において、本発明は、
　上記本発明のタングステン酸のアルカリ金属塩の製造方法を含む、
　パラタングステン酸アンモニウムの製造方法を提供する。 In yet another aspect, the invention is:
The method for producing an alkali metal salt of tungstic acid of the present invention is included.
A method for producing ammonium paratungstate is provided.
　さらに別の側面において、本発明は、
　アルカリ金属炭酸塩と、
　タングステン酸のアルカリ金属塩と、
　タングステンに対して酸化剤として働く金属イオンの還元生成物と、
　を含む、タングステン酸のアルカリ金属塩を含む組成物を提供する。 In yet another aspect, the invention is:
Alkali metal carbonate and
Alkali metal salt of tungstic acid and
Reduction products of metal ions that act as an oxidant for tungsten,
Provided is a composition comprising an alkali metal salt of tungstic acid.
　さらに別の側面において、本発明は、
　タングステン及びコバルトを含み、
　タングステン濃度に対するコバルト濃度の割合が０．５％以下である、
　タングステン酸のアルカリ金属塩を提供する。 In yet another aspect, the invention is:
Contains tungsten and cobalt,
The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less.
Provided are alkali metal salts of tungstic acid.
　さらに別の側面において、本発明は、
　タングステン及びコバルトを含み、
　タングステン濃度に対するコバルト濃度の割合が０．５％以下である、
　パラタングステン酸アンモニウムを提供する。 In yet another aspect, the invention is:
Contains tungsten and cobalt,
The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less.
Provide ammonium paratungstate.
　本発明によれば、安全かつ効率的にタングステンを回収することができる。 According to the present invention, tungsten can be recovered safely and efficiently.
図１は、本発明の一実施形態に係るタングステンの回収方法の工程図である。FIG. 1 is a process diagram of a method for recovering tungsten according to an embodiment of the present invention. 図２Ａは、図１のステップＳ１の工程の模式図である。FIG. 2A is a schematic diagram of the process of step S1 of FIG. 図２Ｂは、酸素イオン種がタングステンを酸化する反応を示す図である。FIG. 2B is a diagram showing a reaction in which an oxygen ion species oxidizes tungsten. 図２Ｃは、炭酸イオンがタングステンを酸化する反応を示す図である。FIG. 2C is a diagram showing a reaction in which carbonate ions oxidize tungsten. 図３は、実施例で用いた反応装置の概略断面図である。FIG. 3 is a schematic cross-sectional view of the reactor used in the examples. 図４は、反応後における実施例１の超硬チップの光学写真である。FIG. 4 is an optical photograph of the cemented carbide chip of Example 1 after the reaction. 図５は、反応後における実施例１の超硬チップのＸＲＤパターンを示す。FIG. 5 shows the XRD pattern of the cemented carbide chip of Example 1 after the reaction. 図６Ａは、反応後における実施例３の超硬チップの光学写真である。FIG. 6A is an optical photograph of the cemented carbide chip of Example 3 after the reaction. 図６Ｂは、反応後における実施例４の超硬チップの光学写真である。FIG. 6B is an optical photograph of the cemented carbide chip of Example 4 after the reaction. 図７Ａは、反応後における実施例３の超硬チップのＸＲＤパターンを示す。FIG. 7A shows the XRD pattern of the carbide chip of Example 3 after the reaction. 図７Ｂは、反応後における実施例４の超硬チップのＸＲＤパターンを示す。FIG. 7B shows the XRD pattern of the carbide chip of Example 4 after the reaction. 図８は、反応後における実施例９，１０，１１及び１２のるつぼ内の光学写真である。FIG. 8 is an optical photograph of the crucibles of Examples 9, 10, 11 and 12 after the reaction.
　以下、本発明の実施形態について、図面を参照しながら説明する。本発明は、以下の実施形態に限定されない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.
　図１は、本発明の一実施形態に係るタングステンの回収方法の工程図である。ステップＳ１の工程は、溶融炭酸塩にタングステン含有材料を酸化溶解させる工程である。言い換えれば、ステップＳ１の工程は、溶融炭酸塩とタングステン含有材料とを接触させる工程である。炭酸塩はアルカリ金属炭酸塩である。この工程によってタングステンが６価まで酸化され、タングステン酸のアルカリ金属塩が得られる。 FIG. 1 is a process diagram of a method for recovering tungsten according to an embodiment of the present invention. The step of step S1 is a step of oxidizing and dissolving the tungsten-containing material in the molten carbonate. In other words, the step of step S1 is a step of bringing the molten carbonate into contact with the tungsten-containing material. The carbonate is an alkali metal carbonate. By this step, tungsten is oxidized to hexavalent to obtain an alkali metal salt of tungstic acid.
　図２Ａは、図１のステップＳ１の工程の模式図である。ステップＳ１の工程では、まず、容器２８に必要な材料を入れる。必要な材料は、アルカリ金属炭酸塩、金属イオン源及びタングステン含有材料２４である。これらの材料を容器２８に入れた後、ヒータ１８で容器２８を加熱すると溶融炭酸塩２２が生成する。溶融炭酸塩２２は、金属イオン源に由来する金属イオン及びアルカリ金属炭酸塩を含む。溶融炭酸塩２２にタングステン含有材料２４が接するように、容器２８にタングステン含有材料２４が収められている。アルカリ金属炭酸塩を溶融させたのち、容器２８に金属イオン源を加えてもよい。アルカリ金属炭酸塩を溶融させたのち、容器２８にタングステン含有材料２４を加えてもよい。 FIG. 2A is a schematic diagram of the process of step S1 of FIG. In the step S1, first, the necessary materials are put into the container 28. The required materials are alkali metal carbonate, metal ion source and tungsten-containing material 24. After putting these materials in the container 28, heating the container 28 with the heater 18 produces molten carbonate 22. The molten carbonate 22 contains a metal ion derived from a metal ion source and an alkali metal carbonate. The tungsten-containing material 24 is contained in the container 28 so that the tungsten-containing material 24 is in contact with the molten carbonate 22. After melting the alkali metal carbonate, a metal ion source may be added to the container 28. After melting the alkali metal carbonate, the tungsten-containing material 24 may be added to the container 28.
　本実施形態によれば、アルカリ金属炭酸塩に由来する酸化力と金属イオン源に由来する酸化力とが重畳的に作用するので、タングステン含有材料２４に含まれたタングステンを効率的に酸化することができる。酸化されたタングステンは、タングステン酸イオンの形で溶融炭酸塩２２に溶解する。酸化溶解反応は速やかに進行するが、爆発的ではない。そのため、粉末状のタングステン含有材料も処理可能である。有毒な排気ガスが生じないので、設備コストが安価であるとともに、環境を汚染することもない。容器２８に高い耐食性が要求されず、容器２８の材料として種々の材料が使用可能である。 According to the present embodiment, since the oxidizing power derived from the alkali metal carbonate and the oxidizing power derived from the metal ion source act in an overlapping manner, the tungsten contained in the tungsten-containing material 24 can be efficiently oxidized. Can be done. The oxidized tungsten dissolves in the molten carbonate 22 in the form of tungstic acid ions. The oxidative dissolution reaction proceeds rapidly, but is not explosive. Therefore, powdered tungsten-containing materials can also be processed. Since no toxic exhaust gas is generated, the equipment cost is low and the environment is not polluted. High corrosion resistance is not required for the container 28, and various materials can be used as the material for the container 28.
　アルカリ金属炭酸塩は、Ｎａ2ＣＯ3、Ｌｉ2ＣＯ3及びＫ2ＣＯ3からなる群より選ばれる少なくとも１つを含む。Ｎａ2ＣＯ3及びＫ2ＣＯ3は安価であるため推奨される。Ｎａ2ＣＯ3の融点は８５１℃である。Ｎａ2ＣＯ3－Ｌｉ2ＣＯ3系の共晶点は４９７℃である。Ｎａ2ＣＯ3－Ｋ2ＣＯ3系の共晶点は７０２℃である。Ｋ2ＣＯ3－Ｌｉ2ＣＯ3系の共晶点は４８８℃である。Ｎａ2ＣＯ3－Ｌｉ2ＣＯ3－Ｋ2ＣＯ3系の共晶点は３９０℃である。そのため、Ｎａ2ＣＯ3に加えてＬｉ2ＣＯ3及び／又はＫ2ＣＯ3を用いるなど、Ｎａ2ＣＯ3、Ｌｉ2ＣＯ3及びＫ2ＣＯ3からなる群より選ばれる２種又は３種を用いると、アルカリ金属炭酸塩の融点が下がり、より低温でのタングステンの回収が可能になり、エネルギー消費の面で有利である。金属イオン源の種類に応じて、アルカリ金属炭酸塩を使い分けてもよい。 The alkali metal carbonate comprises at least one selected from the group consisting of Na 2 CO 3 , Li 2 CO 3 and K 2 CO 3 . Na 2 CO 3 and K 2 CO 3 are recommended due to their low cost. The melting point of Na 2 CO 3 is 851 ° C. The eutectic point of the Na 2 CO 3 − Li 2 CO 3 system is 497 ° C. The eutectic point of the Na 2 CO 3 -K 2 CO 3 system is 702 ° C. The eutectic point of the K 2 CO 3 − Li 2 CO 3 system is 488 ° C. The eutectic point of the Na 2 CO 3 -Li 2 CO 3 -K 2 CO 3 system is 390 ° C. Therefore, 2 or 3 types selected from the group consisting of Na 2 CO 3 , Li 2 CO 3 and K 2 CO 3 , such as using Li 2 CO 3 and / or K 2 CO 3 in addition to Na 2 CO 3 . When used, the melting point of the alkali metal carbonate is lowered, and tungsten can be recovered at a lower temperature, which is advantageous in terms of energy consumption. Alkali metal carbonate may be used properly according to the type of the metal ion source.
　金属イオン源は、アルカリ金属炭酸塩の融液に溶解することによって、タングステンに対して酸化剤として働く金属イオンを供給する。詳細には、金属イオン源は、タングステン含有材料２４に含まれたタングステン成分に対して酸化剤として働く。金属イオン源に由来する金属イオンには、Ｍn+で表される金属イオン（カチオン）だけでなく、ＭＯa b-で表される金属オキソアニオンも含まれる（ａ、ｂ、ｎは正の整数）。金属イオン源に含まれた金属は、アルカリ金属、アルカリ土類金属、ランタノイド及びアクチノイド以外の金属である。なお、本明細書では、Ｓｂのような半金属も「金属」に含まれる。 The metal ion source supplies metal ions that act as an oxidizing agent to tungsten by dissolving in a melt of an alkali metal carbonate. Specifically, the metal ion source acts as an oxidant for the tungsten component contained in the tungsten-containing material 24. The metal ion derived from the metal ion source includes not only the metal ion (cation) represented by M n + but also the metal oxo anion represented by MO a b- (a, b, n are positive integers). ). The metals contained in the metal ion source are metals other than alkali metals, alkaline earth metals, lanthanides and actinides. In addition, in this specification, a metalloid such as Sb is also included in "metal".
　金属イオン源は、ＮＯxを発生させず、かつ、タングステンに対して酸化剤として働く金属イオンを供給しうる金属化合物でありうる。そのような金属化合物としては、金属酸化物、金属炭酸塩、金属硫酸塩などが挙げられる。金属化合物は、望ましくは、金属酸化物及び金属炭酸塩からなる群より選ばれる少なくとも１つを含む。 The metal ion source can be a metal compound that does not generate NO x and can supply metal ions that act as an oxidizing agent for tungsten. Examples of such metal compounds include metal oxides, metal carbonates, metal sulfates and the like. The metal compound preferably comprises at least one selected from the group consisting of metal oxides and metal carbonates.
　例えば、金属酸化物は、下記式（１ａ）の酸性溶解又は（１ｂ）の塩基性溶解に従ってアルカリ金属炭酸塩の融液に溶解する。金属酸化物に由来する金属イオンは、下記式（２ａ）又は（２ｂ）に従ってタングステン含有材料２４に含まれたタングステンを酸化する。金属イオンは還元されて単体金属などの還元生成物２６へと変化する。金属酸化物は、アルカリ金属炭酸塩の融液に溶解して金属イオン及び酸化物イオンを生じさせる。金属イオン及び酸化物イオンの両方が酸化剤として働くうえ、不要なイオンが溶融炭酸塩中に生じない。不要なイオンは溶融炭酸塩２２への酸化物及びタングステン酸のアルカリ金属塩の溶解度を下げるおそれがある。また、還元生成物２６を酸化することによって金属酸化物を生成させてもよい（後述するステップＳ８）。得られた金属酸化物は、酸化剤として再利用することができる。金属酸化物は、複合酸化物であってもよい。下記式において、ａ、ｂ、ｐ、ｑ、ｒ及びｘは、それぞれ、正の整数を表す。 For example, the metal oxide is dissolved in the melt of the alkali metal carbonate according to the acidic dissolution of the following formula (1a) or the basic dissolution of (1b). The metal ion derived from the metal oxide oxidizes the tungsten contained in the tungsten-containing material 24 according to the following formula (2a) or (2b). The metal ion is reduced and changed to a reduction product 26 such as a simple substance metal. The metal oxide dissolves in a melt of an alkali metal carbonate to generate metal ions and oxide ions. Both metal ions and oxide ions act as oxidants, and unnecessary ions are not generated in the molten carbonate. Unwanted ions may reduce the solubility of oxides and alkali metal salts of tungstic acid in the molten carbonate 22. Further, a metal oxide may be produced by oxidizing the reduction product 26 (step S8 described later). The obtained metal oxide can be reused as an oxidizing agent. The metal oxide may be a composite oxide. In the following equation, a, b, p, q, r and x each represent a positive integer.
　ＭＯx→Ｍn+＋ｘＯ2- ・・・（１ａ）
　ＭＯx＋ｐＯ2-→ＭＯa b- ・・・（１ｂ）
　Ｗ＋（６／ｎ）Ｍn+＋４Ｏ2-→ＷＯ4 2-＋（６／ｎ）Ｍ ・・・（２ａ）
　ｑＷ＋ｒＭＯa b-→ｑＷＯ4 2-＋ｒＭ＋（ａｒ－４ｑ）Ｏ2-・・・（２ｂ） MO x → M n + + xO 2-・ ・ ・ (1a)
MO x + pO 2- → MO a b -... (1b)
W + (6 / n) M n + + 4O 2- → WO 4 2- + (6 / n) M ・ ・ ・ (2a)
qW + rMO a b- → qWO 4 2- + rM + (ar-4q) O 2- ... (2b)
　ＣｕＣＯ3、ＦｅＣＯ3などの金属炭酸塩は、常温では化合物として存在する。しかし、高温のアルカリ金属炭酸塩の融液に溶解すると、例えば下記式（３ａ）及び（３ｂ）に従って熱分解する。金属酸化物は、上記式（１ａ）に従ってアルカリ金属炭酸塩の融液に溶解する。ＣＯ2は、ガスとして周囲雰囲気に拡散する。つまり、金属炭酸塩を用いた場合には、金属酸化物を用いた場合と同じ結果が得られる。 Metallic carbonates such as CuCO 3 and FeCO 3 exist as compounds at room temperature. However, when it is dissolved in a high-temperature alkali metal carbonate melt, it is thermally decomposed according to the following formulas (3a) and (3b), for example. The metal oxide is dissolved in the melt of the alkali metal carbonate according to the above formula (1a). CO 2 diffuses into the surrounding atmosphere as a gas. That is, when a metal carbonate is used, the same result as when a metal oxide is used can be obtained.
　ＣｕＣＯ3→ＣｕＯ＋ＣＯ2 ・・・（３ａ）
　ＦｅＣＯ3→ＦｅＯ＋ＣＯ2 ・・・（３ｂ） CuCO 3 → CuO + CO 2 ... (3a)
FeCO 3 → FeO + CO 2 ... (3b)
　金属イオンＭn+が０価まで完全に還元されることは必須ではない。金属イオンＭn+は、より小さい価数を持つＭm+（ｎ＞ｍ）まで還元されてもよい。この場合、金属酸化物に由来する金属イオンは、下記式（２ｃ）又は（２ｄ）に従ってタングステン含有材料２４に含まれたタングステンを酸化する。下記式において、ａ、ｂ、ｃ、ｄ、ｐ、ｑ、ｍ及びｎは、それぞれ、正の整数を表す。 It is not essential that the metal ion M n + is completely reduced to zero valence. The metal ion M n + may be reduced to M m + (n> m) having a smaller valence. In this case, the metal ion derived from the metal oxide oxidizes the tungsten contained in the tungsten-containing material 24 according to the following formula (2c) or (2d). In the following equation, a, b, c, d, p, q, m and n each represent a positive integer.
　Ｗ＋（６／（ｎ－ｍ））Ｍn+＋４Ｏ2-→ＷＯ4 2-＋（６／（ｎ－ｍ））Ｍm+（２ｃ）
　ｐＷ＋ｑＭＯa b-→ｐＷＯ4 2-＋ｑＭＯc d-＋（ａｑ－ｃｑ－４ｐ）Ｏ2-  （２ｄ） W + (6 / (nm)) M n + + 4O 2- → WO 4 2- + (6 / (nm)) M m + (2c)
pW + qMO a b- → pWO 4 2- + qMO c d- + (aq-cq-4p) O 2- (2d)
　図２Ａには、タングステンの酸化溶解反応が示されている。炭化タングステン等のタングステン化合物を用いた場合も上記式（２ａ）から（２ｄ）に準ずる反応によってタングステンが酸化されて溶融炭酸塩２２に溶解する。 FIG. 2A shows the oxidation-dissolution reaction of tungsten. Even when a tungsten compound such as tungsten carbide is used, tungsten is oxidized by a reaction according to the above formulas (2a) to (2d) and dissolved in the molten carbonate 22.
　金属イオン源から供給されるべき金属イオンは、Ｃｕイオン、Ｆｅイオン、Ｎｉイオン、Ｓｎイオン、Ｍｎイオン、Ｖイオン、Ｐｂイオン、Ｓｂイオン、及びＣｏイオンからなる群より選ばれる少なくとも１つを含んでいてもよい。これらの金属イオンは、タングステンを酸化させることができる。 The metal ion to be supplied from the metal ion source contains at least one selected from the group consisting of Cu ion, Fe ion, Ni ion, Sn ion, Mn ion, V ion, Pb ion, Sb ion, and Co ion. You may be. These metal ions can oxidize tungsten.
　金属イオン源から供給されるべき金属イオンは、Ｃｕ（＋１）、Ｃｕ（＋２）、Ｆｅ（＋２）、Ｆｅ（＋３）、Ｎｉ（＋２）、Ｓｎ（＋２）、Ｓｎ（＋４）、Ｍｎ（＋２）、Ｍｎ（＋４）、Ｖ（＋２）、Ｖ（＋３）、Ｖ（＋４）、Ｖ（＋５）、Ｐｂ（＋２）、Ｐｂ（＋４）、Ｓｂ（＋３）、Ｓｂ（＋４）、Ｓｂ（＋５）、Ｃｏ（＋２）、及びＣｏ（＋３）からなる群より選ばれる少なくとも１つを含んでいてもよい。これらの金属イオンは、タングステンを酸化させることができる。詳細には、該当溶融炭酸塩下でＭn+／Ｍ又はＭn+／Ｍm+（ｎ＞ｍ）の酸化還元電位がＷの溶出電位よりも貴であれば、その金属イオンは本実施形態において使用可能である。本実施形態によれば、金属イオンの種類によって溶融炭酸塩２２の酸化還元ポテンシャルを制御することができるので、広い表面積を有する粉末状のタングステン含有材料の処理も容易である。 The metal ions to be supplied from the metal ion source are Cu (+1), Cu (+2), Fe (+2), Fe (+3), Ni (+2), Sn (+2), Sn (+4), Mn (+2). ), Mn (+4), V (+2), V (+3), V (+4), V (+5), Pb (+2), Pb (+4), Sb (+3), Sb (+4), Sb (+5) ), Co (+2), and Co (+3) may contain at least one selected from the group. These metal ions can oxidize tungsten. Specifically, if the redox potential of M n + / M or M n + / M m + (n> m) under the relevant molten carbonate is noble than the elution potential of W, the metal ion is used in this embodiment. It is possible. According to this embodiment, since the redox potential of the molten carbonate 22 can be controlled by the type of metal ion, it is easy to treat a powdered tungsten-containing material having a large surface area.
　なお、従来の溶融硝酸塩法において、溶融硝酸塩の酸化還元ポテンシャルは反応で発生するＮＯxで規定されるため、溶融硝酸塩の酸化還元ポテンシャルを制御することは事実上不可能である。 In the conventional molten nitrate method, the redox potential of the molten nitrate is defined by NO x generated in the reaction, so that it is practically impossible to control the redox potential of the molten nitrate.
　上記した金属イオンを供給しうる金属酸化物は、それぞれ、ＣｕＯ、Ｃｕ2Ｏ、ＦｅＯ、Ｆｅ2Ｏ3、ＮｉＯ、ＳｎＯ、ＳｎＯ2、ＭｎＯ、ＭｎＯ2、ＶＯ、Ｖ2Ｏ3、ＶＯ2、Ｖ2Ｏ5、ＰｂＯ、ＰｂＯ2、Ｓｂ2Ｏ3、ＳｂＯ2、Ｓｂ2Ｏ5、ＣｏＯ、及びＣｏ2Ｏ3である。 The metal oxides that can supply the above-mentioned metal ions are CuO, Cu 2 O, FeO, Fe 2 O 3 , NiO, SnO, SnO 2 , MnO, MnO 2 , VO, V 2 O 3 , VO 2 , respectively. V 2 O 5 , PbO, PbO 2 , Sb 2 O 3 , SbO 2 , Sb 2 O 5 , CoO, and Co 2 O 3 .
　金属酸化物は、ＣｕＯ、Ｃｕ2Ｏ、ＶＯ、Ｖ2Ｏ3、ＶＯ2、及びＶ2Ｏ5からなる群より選ばれる少なくとも１つを含んでいてもよい。溶融炭酸塩２２に対する酸化銅の溶解度は高い。そのため、金属酸化物として酸化銅を用いると銅イオン及び酸化物イオンを確実に生じさせることができる。また、金属酸化物に含まれた金属がタングステン含有材料２４に含まれた金属と合金を形成しない場合、下流工程において各金属の分離が容易である。例えば、超硬工具のスクラップにはＣｏが多く含まれている。ＣｕとＣｏとは合金を形成しないので、磁力選別などの既知の方法でＣｕとＣｏとを選別することができる。したがって、超硬工具のスクラップを本実施形態の方法で処理するとき、金属酸化物としてＣｕＯ及び／又はＣｕ2Ｏを用いることが推奨される。また、酸化バナジウムもタングステンを酸化させる力が強いので推奨される。 The metal oxide may contain at least one selected from the group consisting of CuO, Cu2O , VO, V2O3 , VO2 , and V2O5 . The solubility of copper oxide in the molten carbonate 22 is high. Therefore, when copper oxide is used as the metal oxide, copper ions and oxide ions can be reliably generated. Further, when the metal contained in the metal oxide does not form an alloy with the metal contained in the tungsten-containing material 24, the separation of each metal is easy in the downstream process. For example, scrap of cemented carbide tools contains a large amount of Co. Since Cu and Co do not form an alloy, Cu and Co can be sorted by a known method such as magnetic force sorting. Therefore, it is recommended to use CuO and / or Cu 2O as the metal oxide when processing the scrap of the cemented carbide tool by the method of this embodiment. Vanadium oxide is also recommended because it has a strong ability to oxidize tungsten.
　溶融炭酸塩２２を調製するために用いられるアルカリ金属炭酸塩の量は、処理されるべきタングステン含有材料に含まれた１ｍｏｌのタングステンに対して、例えば０．３ｍｏｌ以上２０ｍｏｌ以下である。これにより、タングステンを十分に酸化溶解させることができる。例えば、１ｍｏｌのＮａ2ＣＯ3には、Ｎａ2ＷＯ4が最大で３．３ｍｏｌ溶解する。この観点から、アルカリ金属炭酸塩の量の下限値が決定される。アルカリ金属炭酸塩の量の上限値は、経済性の観点から決定される。 The amount of alkali metal carbonate used to prepare the molten carbonate 22 is, for example, 0.3 mol or more and 20 mol or less with respect to 1 mol of tungsten contained in the tungsten-containing material to be treated. This makes it possible to sufficiently oxidize and dissolve tungsten. For example, a maximum of 3.3 mol of Na 2 WO 4 is dissolved in 1 mol of Na 2 CO 3 . From this point of view, the lower limit of the amount of alkali metal carbonate is determined. The upper limit of the amount of alkali metal carbonate is determined from the viewpoint of economy.
　溶融炭酸塩２２への金属イオン源の添加量は特に限定されない。アルカリ金属炭酸塩の使用量を基準（１００ｍｏｌ％）としたとき、金属イオン源の添加量は、例えば、０．５ｍｏｌ％以上５０ｍｏｌ％以下である。 The amount of the metal ion source added to the molten carbonate 22 is not particularly limited. When the amount of alkali metal carbonate used is used as a reference (100 mol%), the amount of the metal ion source added is, for example, 0.5 mol% or more and 50 mol% or less.
　なお、アルカリ金属炭酸塩に由来する酸化力は、過酸化物イオン（Ｏ2 2-）、超酸化物イオン（Ｏ2 -）及び炭酸イオン（ＣＯ3 2-）によって発揮される。 The oxidizing power derived from the alkali metal carbonate is exerted by peroxide ions (O 2 2- ), superoxide ions (O 2- ) and carbonate ions (CO 3 2- ).
　図２Ｂは、酸素イオン種（Ｏ2 2-，Ｏ2 -）がタングステンを酸化する反応を示す図である。図２Ｃは、炭酸イオン（ＣＯ3 2-）がタングステンを酸化する反応を示す図である。図２Ｂに示すように、酸素イオン種による酸化反応では、雰囲気中のＯ2がＯ2 2-イオン又はＯ2 -イオンとして溶融炭酸塩に化学溶解し、溶融炭酸塩中を拡散した後にタングステンを酸化する。図２Ｃに示すように、炭酸イオンによる酸化反応では、溶融炭酸塩中に存在するＣＯ3 2-が直接タングステンを酸化する。ただし、後述する実施例から明らかとなるように、金属イオン源に由来する酸化力と金属イオン源の溶解度はともに大きいため、金属イオン源による酸化溶解反応は、これらの反応機構による酸化溶解反応よりも支配的に進行する。 FIG. 2B is a diagram showing a reaction in which oxygen ion species (O 2 2- , O 2- ) oxidize tungsten. FIG. 2C is a diagram showing a reaction in which carbonate ions (CO 3 2- ) oxidize tungsten. As shown in FIG. 2B, in the oxidation reaction with oxygen ion species, O 2 in the atmosphere is chemically dissolved in the molten carbonate as O 2 2- ion or O 2 - ion, diffused in the molten carbonate, and then tungsten is formed. Oxidize. As shown in FIG. 2C, in the oxidation reaction with carbonate ions, CO 3 2- present in the molten carbonate directly oxidizes tungsten. However, as will be clear from the examples described later, since both the oxidizing power derived from the metal ion source and the solubility of the metal ion source are large, the oxidative dissolution reaction by the metal ion source is more than the oxidative dissolution reaction by these reaction mechanisms. Also progresses predominantly.
　溶融炭酸塩２２の目標温度は、アルカリ金属炭酸塩の融点に応じて定められる。溶融炭酸塩２２の目標温度は、例えば、５００℃以上１０００℃以下である。目標温度は、７００℃以上９５０℃以下であってもよい。溶融炭酸塩２２の目標温度がこのような範囲にあると、タングステンの酸化溶解反応を十分に進行させることができる。１０００℃以下では容器２８の腐食が起こりにくく、容器２８の材料の選択の幅も広がる。溶融炭酸塩２２の目標温度は、溶融炭酸塩２２への金属イオン源の溶解度を考慮して設定されてもよい。溶融炭酸塩２２に金属イオン源が十分に溶解している場合、酸化剤として働く金属イオンが金属イオン源から十分に供給されるためである。 The target temperature of the molten carbonate 22 is determined according to the melting point of the alkali metal carbonate. The target temperature of the molten carbonate 22 is, for example, 500 ° C. or higher and 1000 ° C. or lower. The target temperature may be 700 ° C. or higher and 950 ° C. or lower. When the target temperature of the molten carbonate 22 is in such a range, the oxidation-dissolution reaction of tungsten can sufficiently proceed. At 1000 ° C. or lower, corrosion of the container 28 is unlikely to occur, and the range of material selection for the container 28 is widened. The target temperature of the molten carbonate 22 may be set in consideration of the solubility of the metal ion source in the molten carbonate 22. This is because when the metal ion source is sufficiently dissolved in the molten carbonate 22, the metal ions acting as an oxidizing agent are sufficiently supplied from the metal ion source.
　溶融炭酸塩２２を目標温度に維持すべき所定時間は特に限定されず、例えば、０時間以上５０時間以下であり、好ましくは２５時間以下、より好ましくは、５時間以下、さらに好ましくは２．５時間以下である。本実施形態によれば、短時間で反応を十分に進行させることができる。「０時間」は、溶融炭酸塩２２の温度を所定の速度で上昇させて溶融炭酸塩２２が目標温度に達した後、直ちに降温過程に移ることを意味する。後述する実施例から明らかなように、この場合でも反応は進行しうる。所定時間にわたって溶融炭酸塩２２を目標温度に維持した後、溶融炭酸塩２２の温度を所定の速度で常温まで低下させてもよい。 The predetermined time for maintaining the molten carbonate 22 at the target temperature is not particularly limited, and is, for example, 0 hours or more and 50 hours or less, preferably 25 hours or less, more preferably 5 hours or less, still more preferably 2.5 hours. It's less than an hour. According to this embodiment, the reaction can be sufficiently advanced in a short time. “0 hours” means that the temperature of the molten carbonate 22 is raised at a predetermined rate, and after the molten carbonate 22 reaches the target temperature, the temperature lowering process is immediately started. As will be clear from the examples described later, the reaction can proceed even in this case. After maintaining the molten carbonate 22 at the target temperature for a predetermined time, the temperature of the molten carbonate 22 may be lowered to room temperature at a predetermined rate.
　タングステン含有材料２４としては、先に説明したように、炭化タングステンを主成分として含む超硬工具のスクラップが挙げられる。超硬工具のスクラップは、超硬工具の形状を保った大きいハードスクラップであってもよく、粉末状のソフトスクラップであってもよく、それらの両方が含まれていてもよい。本実施形態の方法によれば、ハードスクラップ及びソフトスクラップの両方を安全に処理することができる。「主成分」は、質量比で最も多く含まれた成分を意味する。 As the tungsten-containing material 24, as described above, scrap of a cemented carbide tool containing tungsten carbide as a main component can be mentioned. The scrap of the cemented carbide tool may be a large hard scrap that retains the shape of the cemented carbide tool, may be a powdery soft scrap, or may contain both of them. According to the method of the present embodiment, both hard scrap and soft scrap can be safely processed. "Main component" means the component contained most in the mass ratio.
　容器２８の材料は特に限定されず、例えば、アルミナなどのセラミックであってもよく、鉄、ニッケルなどの金属材料であってもよい。特許文献１に記載された溶融硝酸塩法では、耐食性を有する高価な容器が必要である。しかし、本実施形態によれば、そのような制約は無く、容器２８の材料として種々の材料が使用可能である。 The material of the container 28 is not particularly limited, and may be, for example, a ceramic such as alumina, or a metal material such as iron or nickel. The molten nitrate method described in Patent Document 1 requires an expensive container having corrosion resistance. However, according to the present embodiment, there is no such restriction, and various materials can be used as the material of the container 28.
　容器２８が置かれた周囲雰囲気は特に限定されない。周囲雰囲気は、不活性雰囲気であってもよく、酸化雰囲気であってもよい。不活性雰囲気には、希ガス、Ｎ2ガスなどの不活性ガスが用いられる。酸化雰囲気としては、Ｏ2ガスなどの酸化剤ガスを含む雰囲気が挙げられる。不活性ガスと酸化剤ガスとの混合ガスが雰囲気ガスとして使用されてもよい。混合ガスにおける各成分の分圧は適切に調節される。周囲雰囲気の圧力は特に限定されず、大気圧に概ね等しくてもよい。 The surrounding atmosphere in which the container 28 is placed is not particularly limited. The ambient atmosphere may be an inert atmosphere or an oxidizing atmosphere. An inert gas such as a noble gas or N 2 gas is used for the inert atmosphere. Examples of the oxidizing atmosphere include an atmosphere containing an oxidizing agent gas such as O 2 gas. A mixed gas of the inert gas and the oxidant gas may be used as the atmospheric gas. The partial pressure of each component in the mixed gas is adjusted appropriately. The pressure of the ambient atmosphere is not particularly limited and may be substantially equal to the atmospheric pressure.
　溶融炭酸塩２２が接する雰囲気ガスはＣＯ2ガスを含んでいてもよい。典型的には、希ガスとＣＯ2ガスとの混合ガスが雰囲気ガスとして使用されうる。各ガスの分圧は特に限定されない。ＣＯ2ガスの分圧は、例えば、１×１０-7ａｔｍ以上１ａｔｍ以下であり、好ましくは１×１０-4ａｔｍ以上０．８ａｔｍ以下である。ＣＯ2ガスの分圧の下限値は、大気を別のガスで希釈した際に想定される値に基づいて定められる。ＣＯ2ガスの分圧の下限値は、純ＣＯ2ガスにＯ2ガスなどの他のガスを添加した際に想定される値に基づいて定められる。ＣＯ2ガスの分圧を調節することによって、溶融炭酸塩２２の塩基度を制御することが可能である。これにより、酸化溶解反応の反応速度を制御することができる。ＣＯ2ガスの分圧を調節することによって、溶融炭酸塩２２への金属イオン源の溶解度、及び、溶融炭酸塩２２へのタングステン酸のアルカリ金属塩の溶解度を調節することも可能である。ＣＯ2ガスの分圧は、金属イオンの種類に応じて調節されてもよい。 The atmospheric gas with which the molten carbonate 22 is in contact may contain CO 2 gas. Typically, a mixed gas of a noble gas and a CO 2 gas can be used as the atmospheric gas. The partial pressure of each gas is not particularly limited. The partial pressure of the CO 2 gas is, for example, 1 × 10 -7 atm or more and 1 atm or less, preferably 1 × 10 -4 atm or more and 0.8 atm or less. The lower limit of the partial pressure of CO 2 gas is determined based on the value assumed when the atmosphere is diluted with another gas. The lower limit of the partial pressure of CO 2 gas is determined based on the value assumed when another gas such as O 2 gas is added to pure CO 2 gas. By adjusting the partial pressure of the CO 2 gas, it is possible to control the basicity of the molten carbonate 22. Thereby, the reaction rate of the oxidative dissolution reaction can be controlled. By adjusting the partial pressure of the CO 2 gas, it is also possible to adjust the solubility of the metal ion source in the molten carbonate 22 and the solubility of the alkali metal salt of tungsten acid in the molten carbonate 22. The partial pressure of the CO 2 gas may be adjusted according to the type of metal ion.
　なお、従来の溶融硝酸塩法において、溶融硝酸塩の塩基度は反応で発生するＮＯxで規定されるため、溶融硝酸塩の塩基度を制御することは事実上不可能である。 In the conventional molten nitrate method, the basicity of the molten nitrate is defined by NO x generated in the reaction, so that it is practically impossible to control the basicity of the molten nitrate.
　ステップＳ１の工程において、溶融炭酸塩２２を撹拌してもよい。超硬工具チップの表面には金属イオン源に由来する金属が堆積する。撹拌によって、チップの表面から堆積した金属を脱落させることができる。これにより、タングステンの酸化溶解反応をよりスムーズに進行させることができる。 The molten carbonate 22 may be stirred in the step S1. Metals derived from metal ion sources are deposited on the surface of the carbide tool tip. By stirring, the metal deposited from the surface of the chip can be removed. As a result, the oxidation-dissolution reaction of tungsten can proceed more smoothly.
　ステップＳ１の工程において、Ｏ2ガスを溶融炭酸塩２２にバブリングしてもよい。これにより、溶融炭酸塩２２に酸素イオン種（Ｏ2 2-，Ｏ2 -）を供給できるので、図２Ｂを参照して説明した反応を促進することができる。また、タングステンを酸化した後の金属をＯ2ガスが再び酸化することによって、酸化剤としての金属イオンを再生できる可能性がある。 In the step S1, O 2 gas may be bubbled to the molten carbonate 22. As a result, oxygen ion species (O 2 2- , O 2- ) can be supplied to the molten carbonate 22, so that the reaction described with reference to FIG. 2B can be promoted. In addition, there is a possibility that metal ions as an oxidizing agent can be regenerated by the O 2 gas reoxidizing the metal after oxidizing tungsten.
　溶融炭酸塩２２の温度を常温まで下げて容器２８の内容物を固化させると、タングステン酸のアルカリ金属塩を含む組成物が得られる。組成物は、タングステン酸のアルカリ金属塩、未反応のアルカリ金属炭酸塩、及び、金属イオン源に由来する金属イオンの還元生成物２６を含む。還元生成物２６は、典型的には単体金属を含み、ＮａＶＯ2などの塩を含んでいてもよく、これら両方を含んでいてもよい。組成物は、さらに、未反応のタングステン含有材料２４、及び、副生成物を含んでいてもよい。副生成物は、金属残渣、アルカリ金属酸化物などを含む。金属残渣は、タングステン含有材料に含まれる他の金属などを含む。タングステン含有材料２４が超硬工具のスクラップであるとき、他の金属としては、Ｃｏ及びＴａが挙げられる。 When the temperature of the molten carbonate 22 is lowered to room temperature to solidify the contents of the container 28, a composition containing an alkali metal salt of tungstic acid can be obtained. The composition comprises an alkali metal salt of tungsten acid, an unreacted alkali metal carbonate, and a reduction product 26 of the metal ion derived from the metal ion source. The reduction product 26 typically contains a simple metal, may contain a salt such as NaVO 2 , or may contain both. The composition may further contain an unreacted tungsten-containing material 24 and by-products. By-products include metal residues, alkali metal oxides and the like. The metal residue contains other metals contained in the tungsten-containing material and the like. When the tungsten-containing material 24 is scrap of a cemented carbide tool, other metals include Co and Ta.
　タングステン酸のアルカリ金属塩を含む組成物は、例えば、粉末状である。組成物の粉末Ｘ線回折測定を行うと、アルカリ金属炭酸塩、及び、タングステン酸のアルカリ金属塩の存在を確認できる。誘導結合プラズマ発光分光分析によって、金属イオン源に由来する単体金属などの存在を確認できる。以下に説明するように、タングステン酸のアルカリ金属塩を含む組成物に水を加えるだけで、タングステン酸のアルカリ金属塩の水溶液を容易に得ることができる。また、タングステン酸のアルカリ金属塩を含む組成物は、保管性及び運搬性に優れる。そのため、組成物を別の場所に運搬して下流工程を実施してもよい。 The composition containing the alkali metal salt of tungstic acid is, for example, in the form of powder. By performing powder X-ray diffraction measurement of the composition, the presence of the alkali metal carbonate and the alkali metal salt of tungsten acid can be confirmed. The presence of elemental metals derived from metal ion sources can be confirmed by inductively coupled plasma emission spectroscopy. As described below, an aqueous solution of the alkali metal salt of tungsten acid can be easily obtained only by adding water to the composition containing the alkali metal salt of tungsten acid. Further, the composition containing the alkali metal salt of tungstic acid is excellent in storage and transportability. Therefore, the composition may be transported to another location to carry out the downstream process.
　次に、図１のステップＳ２に示すように、容器２８に水を加え、タングステン酸のアルカリ金属塩を含む組成物を水に溶解させる。これにより、タングステン酸のアルカリ金属塩を含む水溶液が得られる。水に溶解しない物質は固形物として沈殿する。また、水溶液のｐＨを適宜調節してもよい。タングステン酸のアルカリ金属塩は、中性又はアルカリ性で水によく溶ける。 Next, as shown in step S2 of FIG. 1, water is added to the container 28, and the composition containing the alkali metal salt of tungstic acid is dissolved in water. This gives an aqueous solution containing an alkali metal salt of tungstic acid. Substances that are insoluble in water precipitate as solids. Further, the pH of the aqueous solution may be appropriately adjusted. Alkali metal salts of tungstic acid are neutral or alkaline and are well soluble in water.
　従来の溶融硝酸塩法において、タングステン酸のアルカリ金属塩を含む水溶液は弱酸性である。これに対し、本実施の形態の溶融炭酸塩法によれば、弱アルカリ性の水溶液が得られる。そのため、タングステン以外の成分の溶解度が低く、より不純物濃度の低いタングステン水溶液を得ることができる。 In the conventional molten nitrate method, the aqueous solution containing the alkali metal salt of tungstic acid is weakly acidic. On the other hand, according to the molten carbonate method of the present embodiment, a weakly alkaline aqueous solution can be obtained. Therefore, it is possible to obtain a tungsten aqueous solution having a low solubility of components other than tungsten and a lower impurity concentration.
　すなわち、本実施の形態の方法で得られたタングステン酸のアルカリ金属塩において、タングステン濃度Ｍ１（単位：質量ｐｐｍ）に対するコバルト濃度Ｍ２（単位：質量ｐｐｍ）の割合（Ｍ２／Ｍ１）は、百分率で表して、好ましくは０．５％以下であり、より好ましくは０．２５％以下である。割合（Ｍ２／Ｍ１）の下限値は特に限定されず、例えば、０．０００１％であり、検出下限以下の可能性もある。 That is, in the alkali metal salt of tungsten acid obtained by the method of the present embodiment, the ratio (M2 / M1) of the cobalt concentration M2 (unit: mass ppm) to the tungsten concentration M1 (unit: mass ppm) is a percentage. In representative, it is preferably 0.5% or less, and more preferably 0.25% or less. The lower limit of the ratio (M2 / M1) is not particularly limited, and is, for example, 0.0001%, which may be equal to or lower than the lower limit of detection.
　次に、図１のステップＳ３に示すように、タングステン酸のアルカリ金属塩を含む水溶液の固液分離を行う。この工程によって、水溶液から水に不溶な沈殿物（例えば、Ｃｕ、Ｃｏ、Ｔａなど）を分離することができる。固液分離の方法は特に限定されず、ろ過、遠心分離、沈殿などの既知の方法が採用されうる。 Next, as shown in step S3 of FIG. 1, solid-liquid separation of an aqueous solution containing an alkali metal salt of tungstic acid is performed. By this step, a water-insoluble precipitate (eg, Cu, Co, Ta, etc.) can be separated from the aqueous solution. The method of solid-liquid separation is not particularly limited, and known methods such as filtration, centrifugation, and precipitation can be adopted.
　なお、ステップＳ８では、ステップＳ３で回収した沈殿物からステップＳ１で用いた金属を回収する。回収した金属を酸化させて金属酸化物を得る。得られた金属酸化物はステップＳ１の工程で再利用できるので経済的である。 In step S8, the metal used in step S1 is recovered from the precipitate recovered in step S3. The recovered metal is oxidized to obtain a metal oxide. The obtained metal oxide can be reused in the step S1 and is economical.
　次に、図１のステップＳ４に示すように、イオン交換樹脂を用いたイオン交換によってタングステン酸のアルカリ金属塩を含む水溶液を処理する。この工程によって、アルカリ金属イオンがアンモニウムイオンで置換され、タングステン酸アンモニウム（（ＮＨ4）2ＷＯ4）水溶液が得られる。 Next, as shown in step S4 of FIG. 1, an aqueous solution containing an alkali metal salt of tungsten acid is treated by ion exchange using an ion exchange resin. By this step, the alkali metal ion is replaced with ammonium ion, and an aqueous solution of ammonium tungstate ((NH 4 ) 2 WO 4 ) is obtained.
　次に、図１のステップＳ５に示すように、タングステン酸アンモニウム水溶液を濃縮してパラタングステン酸アンモニウム（ＡＰＴ：Ammonium paratungstate）を晶出させる。パラタングステン酸アンモニウムにおいて、タングステン濃度ｍ１（単位：質量ｐｐｍ）に対するコバルト濃度ｍ２（単位：質量ｐｐｍ）の割合（ｍ２／ｍ１）は、百分率で表して、好ましくは０．５％以下であり、より好ましくは０．２５％以下である。割合（ｍ２／ｍ１）の下限値は特に限定されず、例えば、０．０００１％であり、検出下限以下の可能性もある。 Next, as shown in step S5 of FIG. 1, the ammonium paratungate aqueous solution is concentrated to crystallize ammonium paratungate (APT: Ammonium paratungstate). In ammonium paratungstate, the ratio (m2 / m1) of the cobalt concentration m2 (unit: mass ppm) to the tungsten concentration m1 (unit: mass ppm) is preferably 0.5% or less in terms of percentage, and more. It is preferably 0.25% or less. The lower limit of the ratio (m2 / m1) is not particularly limited, and is, for example, 0.0001%, which may be equal to or lower than the detection lower limit.
　次に、図１のステップＳ６に示すように、パラタングステン酸アンモニウムを乾燥及び焙焼する。これにより、酸化タングステン（ＷＯ3）が得られる。 Next, as shown in step S6 of FIG. 1, ammonium paratungstate is dried and roasted. This gives tungsten oxide (WO 3 ).
　最後に、図１のステップＳ７に示すように、酸化タングステンを還元する。これにより、金属タングステン（Ｗ）が得られる。酸化タングステンの還元は、水素還元などの既知の方法で行われる。 Finally, as shown in step S7 of FIG. 1, the tungsten oxide is reduced. As a result, metallic tungsten (W) is obtained. The reduction of tungsten oxide is carried out by a known method such as hydrogen reduction.
　溶融炭酸塩法によって超硬チップからタングステンをタングステン酸のアルカリ金属塩として回収する過程において、金属酸化物が酸化剤として機能するかどうかを確かめるために、以下の実験を行った。 The following experiment was conducted to confirm whether the metal oxide functions as an oxidizing agent in the process of recovering tungsten as an alkali metal salt of tungsten acid from the super hard chip by the molten carbonate method.
（予備実験）
　Ａｒ－Ｏ2（０．２ａｔｍ）－ＣＯ2（６．０×１０-4ａｔｍ）雰囲気下、１１７３Ｋの溶融Ｎａ2ＣＯ3浴中で、Ｗ線、Ｆｅ線、Ｃｕ線又はＣｏ線を作用極に用い、Ａｕ線を参照極に用いて浸漬電位を測定した。雰囲気の全圧は１ａｔｍであった。浸漬電位は、雰囲気のガス分圧条件におけるＯ2／Ｏ2-平衡電位により較正した。浸漬電位は、表１に示す反応の酸化還元電位を示すと予想される。Ｃｕ（Ｉ）／Ｃｕ、Ｆｅ（ＩＩ）／Ｆｅ及びＣｏ（ＩＩ）／Ｃｏの酸化還元電位はＷ（ＶＩ）／Ｗの酸化還元電位である－０．９４Ｖよりも貴である。そのため、Ｃｕ（Ｉ）、Ｆｅ（ＩＩ）又はＣｏ（ＩＩ）を溶融炭酸塩に添加すると下記の反応が起こり、超硬工具のスクラップに含まれた炭化タングステンからタングステン成分を酸化溶出できることが予想された。 (Preliminary experiment)
Under the atmosphere of Ar-O 2 (0.2 atm) -CO 2 (6.0 × 10 -4 atm), W line, Fe line, Cu line or Co line is applied in a molten Na 2 CO 3 bath of 1173K. The immersion potential was measured using Au wire as a reference electrode. The total pressure of the atmosphere was 1 atm. The immersion potential was calibrated by the O 2 / O 2- equilibrium potential under atmospheric gas partial pressure conditions. The immersion potential is expected to indicate the redox potential of the reactions shown in Table 1. The redox potentials of Cu (I) / Cu, Fe (II) / Fe and Co (II) / Co are noble than the redox potential of W (VI) / W of -0.94V. Therefore, when Cu (I), Fe (II) or Co (II) is added to the molten carbonate, the following reaction occurs, and it is expected that the tungsten component can be oxidatively eluted from the tungsten carbide contained in the scrap of the cemented carbide tool. rice field.
　６Ｃｕ（Ｉ）＋Ｗ→Ｗ（ＶＩ）＋６Ｃｕ
　３Ｆｅ（ＩＩ）＋Ｗ→Ｗ（ＶＩ）＋３Ｆｅ
　３Ｃｏ（ＩＩ）＋Ｗ→Ｗ（ＶＩ）＋３Ｃｏ 6Cu (I) + W → W (VI) + 6Cu
3Fe (II) + W → W (VI) + 3Fe
3Co (II) + W → W (VI) + 3Co
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
（反応装置の構成）
　図３は、実施例で用いた反応装置の概略断面図である。反応装置１０は、アルミナ製の反応管１１、ステンレス蓋１２及び電気炉１７を備えている。反応管１１がステンレス蓋１２によって閉じられている。反応管１１は電気炉１７に入れられている。ステンレス蓋１２には、入口ポート１３及び出口ポート１４が設けられている。入口ポート１３に供給管１５が取り付けられている。出口ポート１４に排気管１６が取り付けられている。供給管１５及び排気管１６を通じて反応管１１の内部の雰囲気を調節することができる。反応管１１の内部には、るつぼ２０が配置されている。るつぼ２０の中に溶融炭酸塩２２及びタングステン含有材料２４が配置されている。反応管１１を加熱することによって原料から溶融炭酸塩２２が生じ、反応が進行する。 (Structure of reactor)
FIG. 3 is a schematic cross-sectional view of the reactor used in the examples. The reaction apparatus 10 includes a reaction tube 11 made of alumina, a stainless steel lid 12, and an electric furnace 17. The reaction tube 11 is closed by the stainless steel lid 12. The reaction tube 11 is housed in an electric furnace 17. The stainless steel lid 12 is provided with an inlet port 13 and an outlet port 14. A supply pipe 15 is attached to the inlet port 13. An exhaust pipe 16 is attached to the outlet port 14. The atmosphere inside the reaction tube 11 can be adjusted through the supply pipe 15 and the exhaust pipe 16. A crucible 20 is arranged inside the reaction tube 11. The molten carbonate 22 and the tungsten-containing material 24 are arranged in the crucible 20. By heating the reaction tube 11, molten carbonate 22 is generated from the raw material, and the reaction proceeds.
（実施例１）
　溶融炭酸塩の原料として、乳鉢及び乳棒により解砕したＮａ2ＣＯ3粉末（富士フイルム和光純薬社製）と、酸化剤となる金属酸化物とを、アルミナ製のるつぼ（ニッカトー社製，ＳＳＡ－Ｓ，外径３７ｍｍ×高さ２５ｍｍ）に充填した。Ｎａ2ＣＯ3の量は３．１ｇとし、溶解時における溶融塩の深さが６ｍｍとなるように調節した。金属酸化物として、Ｃｕ2Ｏ（富士フイルム和光純薬社製）を用いた。Ｎａ2ＣＯ3の使用量を基準（１００ｍｏｌ％）として、Ｃｕ2Ｏの添加量は、６．４ｍｏｌ％であった。Ｎａ2ＣＯ3粉末及び金属酸化物を充填したるつぼを１８０℃の真空オーブン内で一晩乾燥して、残留水分を除去した。 (Example 1)
As raw materials for molten carbonate, Na 2 CO 3 powder (manufactured by Fujifilm Wako Junyaku Co., Ltd.) crushed by a mortar and pestle and a metal oxide used as an oxidant are used in an alumina crucible (manufactured by Nikkato Corporation, SSA). -S, outer diameter 37 mm x height 25 mm) was filled. The amount of Na 2 CO 3 was 3.1 g, and the depth of the molten salt at the time of dissolution was adjusted to 6 mm. Cu 2 O (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide. Based on the amount of Na 2 CO 3 used (100 mol%), the amount of Cu 2 O added was 6.4 mol%. The crucible filled with Na 2 CO 3 powder and metal oxide was dried overnight in a vacuum oven at 180 ° C. to remove residual water.
　次に、るつぼ内のＮａ2ＣＯ3粉末へ超硬チップ（大昭和精機社製，ＴＰＧ０７０２０２ＦＮ，４５０ｍｇ）を包埋して静置した。その後、図３を参照して説明したように、反応管（外径８０ｍｍ×内径７０ｍｍ×長さ５００ｍｍ）及びステンレス蓋を有する気密容器の中にるつぼを入れて静置した。ステンレス蓋の各ポートには、Ｏリングにより供給管及び排気管を固定した。Ｏリングの劣化を防ぐためにステンレス蓋を冷却ファンで空冷した。反応管を横型電気炉（光洋サーモシステム社製，ＫＴＦ０４０Ｎ１）へ挿入後、常温から５℃／ｍｉｎで昇温を行い、９００℃に達した後、２５時間保持することで反応を進行させた。供給管及び排気管としてアルミナ保護管（ニッカトー社製，ＳＳＡ－Ｓ，外径６．０ｍｍ×内径４．０ｍｍ）を用いた。マスフローコントローラー（堀場エステック社製）で流量制御されたＡｒガス（京都帝酸社製，高純度アルゴン，＞９９．９９８％）及びＣＯ2ガス（京都帝酸社製，高純度炭酸ガス）の混合ガスを全流量５０ｍＬ／ｍｉｎで供給し、反応管の内部をＡｒ－ＣＯ2雰囲気に維持した。Ａｒ－ＣＯ2雰囲気におけるＣＯ2分圧は０．８ａｔｍであった。以下の全ての実施例及び比較例において、Ａｒ－ＣＯ2雰囲気の全圧は１ａｔｍであった。 Next, a cemented carbide chip (TPG070202FN, 450 mg, manufactured by Daishowa Seiki Co., Ltd.) was embedded in Na 2 CO 3 powder in a crucible and allowed to stand. Then, as described with reference to FIG. 3, a crucible was placed in an airtight container having a reaction tube (outer diameter 80 mm × inner diameter 70 mm × length 500 mm) and a stainless steel lid and allowed to stand. A supply pipe and an exhaust pipe were fixed to each port of the stainless steel lid by an O-ring. The stainless steel lid was air-cooled with a cooling fan to prevent deterioration of the O-ring. After inserting the reaction tube into a horizontal electric furnace (KTF040N1 manufactured by Koyo Thermo System Co., Ltd.), the temperature was raised from room temperature at 5 ° C./min, and after reaching 900 ° C., the reaction was allowed to proceed for 25 hours. Alumina protection pipes (manufactured by Nikkato Corporation, SSA-S, outer diameter 6.0 mm x inner diameter 4.0 mm) were used as the supply pipe and the exhaust pipe. Mixing of Ar gas (manufactured by Kyoto Teiko Co., Ltd., high-purity argon,> 99.998%) and CO 2 gas (manufactured by Kyoto Teiko Co., Ltd., high-purity carbon dioxide gas) whose flow control is controlled by a mass flow controller (manufactured by Horiba STEC). The gas was supplied at a total flow rate of 50 mL / min, and the inside of the reaction tube was maintained in an Ar-CO 2 atmosphere. The CO 2 partial pressure in the Ar-CO 2 atmosphere was 0.8 atm. In all the following examples and comparative examples, the total pressure of the Ar-CO 2 atmosphere was 1 atm.
（分析）
　反応の終了後、５℃／ｍｉｎで常温まで冷却を行い、反応管内から超硬チップを回収した。超硬チップは、表面付着物を剥離させた後に重量測定を行い、重量減少率を計算した。結果を表２に示す。 (analysis)
After completion of the reaction, the cemented carbide chips were recovered from the inside of the reaction tube by cooling to room temperature at 5 ° C./min. The weight of the cemented carbide chip was measured after the surface deposits were peeled off, and the weight loss rate was calculated. The results are shown in Table 2.
　得られた塩をタングステンイオンのキレート剤となる酒石酸を含んだ硝酸へ溶解させた後、誘導結合プラズマ発光分光分析（ICP-AES, AMETEK, SPECTROBLUE）でタングステン濃度を分析した。これにより、重量減少率が超硬チップ中の炭化タングステンの酸化溶出であることを確認した。また、得られた塩と残留した超硬チップの相の同定には、Ｘ線回折装置（ＸＲＤ，リガク社製，ＳｍａｒｔＬａｂ，Ｃｕ－Ｋα線，４０ｋＶ，３０ｍＡ）を用いた。 The obtained salt was dissolved in nitrate containing tartrate acid, which is a chelating agent for tungsten ions, and then the tungsten concentration was analyzed by inductively coupled plasma emission spectroscopy (ICP-AES, AMETEK, SPECTROBLUE). From this, it was confirmed that the weight loss rate was the oxidative elution of tungsten carbide in the cemented carbide chip. An X-ray diffractometer (XRD, manufactured by Rigaku, SmartLab, Cu-Kα ray, 40 kV, 30 mA) was used to identify the phase of the obtained salt and the residual cemented carbide chip.
（比較例１）
　Ｃｕ2Ｏを添加しなかったことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表２に示す。 (Comparative Example 1)
The cemented carbide chips were oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that Cu 2 O was not added. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示すように、Ｃｕ2Ｏを添加した実施例１は、比較例１よりも大きい重量減少率を示した。この理由は、Ｃｕ2Ｏが酸化剤として機能し、タングステンの酸化溶出反応が速やかに進行したためである。 As shown in Table 2, Example 1 to which Cu 2 O was added showed a larger weight loss rate than Comparative Example 1. The reason for this is that Cu 2 O functions as an oxidant and the oxidative elution reaction of tungsten proceeds rapidly.
　酸化溶出反応が下記式（Ａ１）で表される場合、言い換えると、Ｃｕイオンが金属Ｃｕまで還元されると仮定した場合、６．４ｍｏｌ％のＣｕ2Ｏは炭化タングステンの重量減少率に換算すると２０．１％に相当する。なお、実際の重量減少率が２０．１％よりも大きい理由は、表面析出物であるＣｕに付着して剥離した部分があるためである。 When the oxidation elution reaction is represented by the following formula (A1), in other words, assuming that Cu ions are reduced to metallic Cu, 6.4 mol% of Cu 2 O is converted into the weight loss rate of tungsten carbide. It corresponds to 20.1%. The reason why the actual weight reduction rate is larger than 20.1% is that there is a portion that adheres to and peels off from Cu, which is a surface precipitate.
　ＷＣ＋４Ｃｕ2Ｏ＋２Ｏ2-→ＷＯ4 2-＋ＣＯ2 2-＋８Ｃｕ・・・（Ａ１） WC + 4Cu 2 O + 2O 2- → WO 4 2- + CO 2 2- + 8Cu ... (A1)
　図４は、反応後における実施例１の超硬チップの光学写真である。図４の左図に示すように、橙赤色の析出物が超硬チップの表面に析出していた。図４の右図に示すように、表面析出物を剥離すると、内側に黒色の未反応チップが残っていた。 FIG. 4 is an optical photograph of the cemented carbide chip of Example 1 after the reaction. As shown in the left figure of FIG. 4, orange-red precipitates were deposited on the surface of the cemented carbide chip. As shown in the right figure of FIG. 4, when the surface precipitate was peeled off, a black unreacted chip remained inside.
　図５は、反応後における実施例１の超硬チップのＸＲＤパターンを示している。図５には、Ｃｕ粉末のＸＲＤパターン及びＣｏ粉末のＸＲＤパターンも併記されている。Ｃｕ粉末のＸＲＤパターン及びＣｏ粉末のＸＲＤパターンとの比較から、析出物は金属Ｃｕであることが確認された。金属Ｃｏの小さいピークは、Ｃｕに付着していた金属Ｃｏに由来するピークである。 FIG. 5 shows the XRD pattern of the cemented carbide chip of Example 1 after the reaction. In FIG. 5, the XRD pattern of Cu powder and the XRD pattern of Co powder are also shown. From the comparison with the XRD pattern of Cu powder and the XRD pattern of Co powder, it was confirmed that the precipitate was metallic Cu. The small peak of the metal Co is a peak derived from the metal Co adhering to Cu.
（実施例２）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表３に示す。 (Example 2)
The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 3.
（比較例２）
　Ｃｕ2Ｏを添加しなかったことを除き、実施例２と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例２と同じ方法で重量減少率を計算した。結果を表３に示す。 (Comparative Example 2)
The cemented carbide chips were oxidatively dissolved by the molten carbonate method in the same manner as in Example 2 except that Cu 2 O was not added. Then, the weight loss rate was calculated by the same method as in Example 2. The results are shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　ＣＯ2分圧を下げてもＣｕ2Ｏの添加により実施例２は大きい重量減少率を示した。ただし、ＣＯ2分圧が高い実施例１は、ＣＯ2分圧が低い実施例２よりも大きい重量減少率を示した。 Even if the partial pressure of CO 2 was lowered, Example 2 showed a large weight loss rate due to the addition of Cu 2 O. However, Example 1 having a high CO 2 partial pressure showed a larger weight loss rate than Example 2 having a low CO 2 partial pressure.
（実施例３）
　金属酸化物として６．４ｍｏｌ％のＦｅＯ（富士フイルム和光純薬社製）を用いたことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表４に示す。 (Example 3)
The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that 6.4 mol% FeO (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 4.
（実施例４）
　金属酸化物として２．１ｍｏｌ％のＦｅ2Ｏ3（富士フイルム和光純薬社製）を用いたことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表４に示す。 (Example 4)
Except for the fact that 2.1 mol% Fe 2 O 3 (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal oxide, the oxidative dissolution treatment of the superhard chip by the molten carbonate method was carried out in the same manner as in Example 1. did. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表４に示すように、ＦｅＯを添加した実施例３及びＦｅ2Ｏ3を添加した実施例４は、比較例１よりも大きい重量減少率を示した。この理由は、ＦｅＯ及びＦｅ2Ｏ3が酸化剤として機能し、酸化溶出反応が速やかに進行したためである。 As shown in Table 4, Example 3 to which FeO was added and Example 4 to which Fe 2O 3 was added showed a larger weight loss rate than that of Comparative Example 1. The reason for this is that FeO and Fe 2 O 3 function as oxidizing agents, and the oxidative elution reaction proceeds rapidly.
　実施例３において、酸化溶出反応が下記式（Ａ２）で表される場合、６．４ｍｏｌ％のＦｅＯは炭化タングステンの重量減少率に換算すると２０．１％に相当する。実施例４において、酸化溶出反応が下記式（Ａ３）で表される場合、２．１ｍｏｌ％のＦｅ2Ｏ3は炭化タングステンの重量減少率に換算すると２０．１％に相当する。 In Example 3, when the oxidative elution reaction is represented by the following formula (A2), 6.4 mol% of FeO corresponds to 20.1% in terms of the weight loss rate of tungsten carbide. In Example 4, when the oxidation elution reaction is represented by the following formula (A3), 2.1 mol% of Fe 2 O 3 corresponds to 20.1% in terms of the weight loss rate of tungsten carbide.
　ＷＣ＋４ＦｅＯ＋２Ｏ2-→ＷＯ4 2-＋ＣＯ2 2-＋４Ｆｅ・・・（Ａ２）
　３ＷＣ＋４Ｆｅ2Ｏ3＋６Ｏ2-→３ＷＯ4 2-＋３ＣＯ2 2-＋８Ｆｅ・・・（Ａ３） WC + 4FeO + 2O 2- → WO 4 2- + CO 2 2- + 4Fe ... (A2)
3WC + 4Fe 2 O 3 + 6O 2- → 3WO 4 2- + 3CO 2 2- + 8Fe ... (A3)
　図６Ａは、反応後における実施例３の超硬チップの光学写真である。図６Ｂは、反応後における実施例４の超硬チップの光学写真である。実施例３及び実施例４の超硬チップの表面のそれぞれに金属光沢を持つ銀色の析出物が析出していた。 FIG. 6A is an optical photograph of the cemented carbide chip of Example 3 after the reaction. FIG. 6B is an optical photograph of the cemented carbide chip of Example 4 after the reaction. Silver-colored precipitates having a metallic luster were deposited on the surfaces of the cemented carbide chips of Examples 3 and 4, respectively.
　図７Ａは、反応後における実施例３の超硬チップのＸＲＤパターンを示している。図７Ｂは、反応後における実施例４の超硬チップのＸＲＤパターンを示している。各ＸＲＤパターンは、Ｆｅのピークを示した。このことから、実施例３及び実施例４における表面析出物は金属Ｆｅであることが確認された。 FIG. 7A shows the XRD pattern of the cemented carbide chip of Example 3 after the reaction. FIG. 7B shows the XRD pattern of the carbide chip of Example 4 after the reaction. Each XRD pattern showed a peak of Fe. From this, it was confirmed that the surface precipitates in Examples 3 and 4 were metallic Fe.
（実施例５）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したことを除き、実施例３と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例３と同じ方法で重量減少率を計算した。結果を表５に示す。 (Example 5)
The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 3 except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 3. The results are shown in Table 5.
（実施例６）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したことを除き、実施例４と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例４と同じ方法で重量減少率を計算した。結果を表５に示す。 (Example 6)
The cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 4 except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm. Then, the weight loss rate was calculated by the same method as in Example 4. The results are shown in Table 5.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　実施例５及び実施例６は、比較例２よりもやや大きい重量減少率を示した。その一方で、実施例５及び実施例６は、実施例３及び実施例４よりも小さい重量減少率を示した。この理由は、低ＣＯ2分圧ではＦｅＯ及びＦｅ2Ｏ3の炭酸塩への溶解度が低いためである。そのため、ＦｅＯ及びＦｅ2Ｏ3を用いる場合には、ＣＯ2分圧の制御が酸化溶解反応を促進するうえでより重要である。 Examples 5 and 6 showed a slightly larger weight loss rate than Comparative Example 2. On the other hand, Examples 5 and 6 showed a smaller weight loss rate than Examples 3 and 4. The reason for this is that FeO and Fe 2 O 3 have low solubility in carbonate at low CO 2 partial pressure. Therefore, when FeO and Fe 2 O 3 are used, the control of the partial pressure of CO 2 is more important for promoting the oxidative dissolution reaction.
（実施例７）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、及び、反応時間を２．５時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表６に示す。 (Example 7)
Except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm and the reaction time was changed to 2.5 hours, the super hard chip by the molten carbonate method was used in the same manner as in Example 1. An oxidative dissolution treatment was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
（実施例８）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏの添加量を１２．８ｍｏｌ％に変更したこと、及び、反応時間を０時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表６に示す。なお、反応時間が０時間であることは、溶融炭酸塩の温度を９００℃まで上昇させた後、直ちに低下させることを意味する。 (Example 8)
Examples except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm, the amount of Cu 2 O added was changed to 12.8 mol%, and the reaction time was changed to 0 hour. The oxidative dissolution treatment of the super hard chip by the molten carbonate method was carried out by the same method as in 1. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6. The reaction time of 0 hours means that the temperature of the molten carbonate is raised to 900 ° C. and then immediately lowered.
（実施例９）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏの添加量を１２．８ｍｏｌ％に変更したこと、及び、反応時間を２．５時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表６に示す。 (Example 9)
Except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm, the amount of Cu 2 O added was changed to 12.8 mol%, and the reaction time was changed to 2.5 hours. The oxidative dissolution treatment of the super hard chip by the molten carbon dioxide method was carried out by the same method as in Example 1. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
　実施例９で得られた塩における誘導結合プラズマ発光分光分析の実測値は、タングステンが４０．７質量ｐｐｍ、コバルトが検出限界である０．０１質量ｐｐｍ以下であった。したがって、アルカリ金属塩における、タングステン濃度に対するコバルト濃度の割合は、０．５％以下（０．２５％以下）であった。また、イオン交換において少なくともタングステン濃度はほぼ変化しないため、パラタングステン酸アンモニウムにおける、タングステン濃度に対するコバルト濃度の割合は、０．５％以下（０．２５％以下）であると容易に類推できる。コバルトは、超硬チップに含まれた結着材に由来し、タングステン酸のアルカリ金属塩及びパラタングステン酸アンモニウムに含まれた不純物である。 The measured values of inductively coupled plasma emission spectroscopy for the salt obtained in Example 9 were 40.7 mass ppm for tungsten and 0.01 mass ppm or less, which is the detection limit for cobalt. Therefore, the ratio of the cobalt concentration to the tungsten concentration in the alkali metal salt was 0.5% or less (0.25% or less). Further, since the tungsten concentration does not change at least in ion exchange, it can be easily inferred that the ratio of the cobalt concentration to the tungsten concentration in ammonium paratungstate is 0.5% or less (0.25% or less). Cobalt is derived from the binder contained in the carbide chip and is an impurity contained in the alkali metal salt of tungstic acid and ammonium paratungstate.
（比較例３）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏを添加しなかったこと、及び、反応時間を０時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表６に示す。 (Comparative Example 3)
Melting by the same method as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm, Cu 2 O was not added, and the reaction time was changed to 0 hours. The oxidative dissolution treatment of the super hard chip by the carbonate method was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
（比較例４）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏを添加しなかったこと、及び、反応時間を２．５時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表６に示す。 (Comparative Example 4)
The same method as in Example 1 except that the partial pressure of CO 2 was changed to 6.0 × 10 -4 atm, Cu 2 O was not added, and the reaction time was changed to 2.5 hours. The oxidative dissolution treatment of the super hard chip was carried out by the molten carbon dioxide method. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 6.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　６．４ｍｏｌ％のＣｕ2Ｏ及び１２．８ｍｏｌ％のＣｕ2Ｏは、それぞれ、炭化タングステンの重量減少率に換算すると２０．１％及び４０．２％に相当する。実施例７及び実施例９における結果から理解できるように、Ｃｕ2Ｏの添加量の増加に伴って重量減少率も増加した。 6.4 mol% Cu 2 O and 12.8 mol% Cu 2 O correspond to 20.1% and 40.2%, respectively, in terms of the weight loss rate of tungsten carbide. As can be understood from the results in Examples 7 and 9, the weight loss rate increased as the amount of Cu 2 O added increased.
　実施例７における重量減少率は、実施例２（表３）における重量減少率に概ね等しかった。このことは、酸化溶解反応が２．５時間でほぼ完了したことを示している。 The weight loss rate in Example 7 was almost equal to the weight loss rate in Example 2 (Table 3). This indicates that the oxidative dissolution reaction was almost completed in 2.5 hours.
　反応時間が０時間の実施例８も８．３％の重量減少率を示した。このことは、昇温及び降温の過程においても酸化溶解反応が進行したことを示している。 Example 8 with a reaction time of 0 hours also showed a weight loss rate of 8.3%. This indicates that the oxidative dissolution reaction proceeded even in the process of raising and lowering the temperature.
（実施例１０）
　ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、超硬チップに代えて炭化タングステン粉末（高純度化学社製，平均粒径１５０μｍ，１００ｍｇ）を用いたこと、Ｃｕ2Ｏの添加量を１２．８ｍｏｌ％に変更したこと、及び、反応時間を２．５時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による炭化タングステン粉末の酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表７に示す。 (Example 10)
The CO 2 partial pressure was changed to 6.0 × 10 -4 atm, and tungsten carbide powder (manufactured by High Purity Chemical Co., Ltd., average particle size 150 μm, 100 mg) was used instead of the super hard chip. Tungsten carbide powder was oxidatively dissolved by the molten carbonate method in the same manner as in Example 1 except that the addition amount was changed to 12.8 mol% and the reaction time was changed to 2.5 hours. .. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 7.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
　反応後、反応管の内部を目視観察し、塩の飛散などが無かったことを確認した。このことは、粉末でも急速な反応による爆発が起こらなかったことを意味する。実施例１０における重量減少率は、比較例４（表６）における重量減少率よりも遥かに大きく、炭化タングステンが粉末であること以外の条件が同一の実施例９（表６）における重量減少率よりも大きかった。 After the reaction, the inside of the reaction tube was visually observed and it was confirmed that there was no salt scattering. This means that even the powder did not explode due to a rapid reaction. The weight loss rate in Example 10 is much larger than the weight loss rate in Comparative Example 4 (Table 6), and the weight loss rate in Example 9 (Table 6) under the same conditions except that the tungsten carbide is a powder is the same. Was bigger than.
（実施例１１）
　Ｎａ2ＣＯ3粉末に代えてＫ2ＣＯ3粉末を炭酸塩として用いたこと、ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏの添加量を１２．８ｍｏｌ％に変更したこと、及び、反応時間を２．５時間に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表８に示す。 (Example 11)
K 2 CO 3 powder was used as a carbonate instead of Na 2 CO 3 powder, the CO 2 partial pressure was changed to 6.0 × 10 -4 atm, and the amount of Cu 2 O added was 12.8 mol%. The oxidative dissolution treatment of the super hard chip by the molten carbonate method was carried out by the same method as in Example 1 except that the reaction time was changed to 2.5 hours. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 8.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　１２．８ｍｏｌ％のＣｕ2Ｏは、炭化タングステンの重量減少率に換算すると４０．２％に相当する。実施例１１における重量減少率は、実施例９（表６）における重量減少率と同程度であった。実施例１１の結果から理解できるように、炭酸塩としてＫ2ＣＯ3を用いた場合にも酸化溶解反応は十分に進行した。 12.8 mol% of Cu 2 O corresponds to 40.2% in terms of the weight loss rate of tungsten carbide. The weight loss rate in Example 11 was about the same as the weight loss rate in Example 9 (Table 6). As can be understood from the results of Example 11, the oxidative dissolution reaction proceeded sufficiently even when K 2 CO 3 was used as the carbonate.
（実施例１２）
　Ｎａ2ＣＯ3粉末とＫ2ＣＯ3粉末との混合物を炭酸塩として用いたこと、ＣＯ2分圧を６．０×１０-4ａｔｍに変更したこと、Ｃｕ2Ｏの添加量を１２．８ｍｏｌ％に変更したこと、反応時間を２．５時間に変更したこと、及び、溶融塩の目標温度を７８０℃に変更したことを除き、実施例１と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表９に示す。 (Example 12)
A mixture of Na 2 CO 3 powder and K 2 CO 3 powder was used as a carbonate, the CO 2 partial pressure was changed to 6.0 × 10 -4 atm, and the amount of Cu 2 O added was 12.8 mol. The super hard chip by the molten carbonate method in the same manner as in Example 1 except that the% was changed, the reaction time was changed to 2.5 hours, and the target temperature of the molten salt was changed to 780 ° C. Oxidation-dissolving treatment was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 9.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　１２．８ｍｏｌ％のＣｕ2Ｏは、炭化タングステンの重量減少率に換算すると４０．２％に相当する。実施例１２における重量減少率は、９００℃の溶融Ｎａ2ＣＯ3を用いた実施例９（表６）よりも低く、９００℃の溶融Ｋ2ＣＯ3を用いた実施例１１（表８）よりも低かった。このことは、Ｎａ2Ｏ－Ｃｕ2Ｏ系の共晶温度が８０６℃であることに関係していると考えられる。つまり、９００℃では溶融塩へのＣｕ2Ｏの溶解度が高いものの、７８０℃では溶融塩へのＣｕ2Ｏの溶解度が低いため、実施例１２における重量減少率が低かったと予想される。この結果から、Ｃｕ2Ｏ又はＣｕＯを用いる場合には、溶融塩の目標温度は、８００℃以上１０００℃以下の範囲に設定することが望ましい。 12.8 mol% of Cu 2 O corresponds to 40.2% in terms of the weight loss rate of tungsten carbide. The weight loss rate in Example 12 was lower than that of Example 9 (Table 6) using molten Na 2 CO 3 at 900 ° C., and from Example 11 (Table 8) using molten K 2 CO 3 at 900 ° C. Was also low. This is considered to be related to the eutectic temperature of the Na 2 O-Cu 2 O system being 806 ° C. That is, it is expected that the weight loss rate in Example 12 was low because the solubility of Cu 2 O in the molten salt was high at 900 ° C., but the solubility of Cu 2 O in the molten salt was low at 780 ° C. From this result, when Cu 2 O or Cu O is used, it is desirable to set the target temperature of the molten salt in the range of 800 ° C. or higher and 1000 ° C. or lower.
　図８は、反応後における実施例９，１０，１１及び１２のるつぼ内の光学写真である。詳細には、図８（ａ）及び図８（ｂ）は、それぞれ、炭酸塩としてＮａ2ＣＯ3のみを含む実施例９及び１０における結果を示している。図８（ｃ）は、炭酸塩としてＫ2ＣＯ3のみを含む実施例１１における結果を示している。図８（ｄ）は、炭酸塩としてＮａ2ＣＯ3及びＫ2ＣＯ3の両方を含む実施例１２における結果を示している。 FIG. 8 is an optical photograph of the crucibles of Examples 9, 10, 11 and 12 after the reaction. In particular, FIGS. 8 (a) and 8 (b) show the results in Examples 9 and 10, respectively, which contain only Na 2 CO 3 as a carbonate. FIG. 8 (c) shows the results in Example 11 containing only K 2 CO 3 as a carbonate. FIG. 8 (d) shows the results in Example 12 containing both Na 2 CO 3 and K 2 CO 3 as carbonates.
　図８（ａ）及び図８（ｂ）に示すように、Ｎａ2ＣＯ3のみを用いた実施例９では超硬チップの表面に金属Ｃｕ（濃い色の部分）が集中的に固着しており、実施例１０ではるつぼの底部に金属Ｃｕ（濃い色の部分）が沈殿していた。一方、図８（ｃ）及び図８（ｄ）に示すように、Ｋ2ＣＯ3を用いた実施例１１及び１２では生成物（主にタングステン酸のアルカリ金属塩）の全体に金属Ｃｕ（濃い色の部分）が分散していた。この原因は、金属Ｃｕの濡れ性及び表面張力の違いであると予想される。超硬チップの表面に固着したＣｕは、イオンの拡散を阻害して酸化溶解反応を遅らせる可能性がある。炭酸塩としてＫ2ＣＯ3を用いると、そのような不利益を回避できる可能性がある。 As shown in FIGS. 8 (a) and 8 (b), in Example 9 using only Na 2 CO 3 , metal Cu (dark colored portion) is intensively adhered to the surface of the cemented carbide chip. In Example 10, metal Cu (dark colored portion) was deposited on the bottom of the crucible. On the other hand, as shown in FIGS. 8 (c) and 8 (d), in Examples 11 and 12 using K 2 CO 3 , the product (mainly the alkali metal salt of tungstic acid) was entirely covered with metallic Cu (dense). The colored part) was dispersed. The cause is expected to be the difference in wettability and surface tension of metallic Cu. Cu adhering to the surface of the cemented carbide chip may inhibit the diffusion of ions and delay the oxidative dissolution reaction. The use of K 2 CO 3 as the carbonate may avoid such disadvantages.
（実施例１３から１６）
　金属酸化物として１２．８ｍｏｌ％のＭｎＯ2、ＳｎＯ2、Ｓｂ2Ｏ3又はＶ2Ｏ5を用いたことを除き、実施例９と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表１０に示す。 (Examples 13 to 16)
Oxidation-dissolution treatment of cemented carbide chips by the molten carbonate method in the same manner as in Example 9 except that 12.8 mol% MnO 2 , SnO 2 , Sb 2 O 3 or V 2 O 5 was used as the metal oxide. Was carried out. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 10.
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000010
　１２．８ｍｏｌ％のＭｎＯ2、ＳｎＯ2、Ｓｂ2Ｏ3、及びＶ2Ｏ5は、それぞれ、炭化タングステンの重量減少率に換算すると、８０．４％、８０．４％、１２０．６％、及び２０１％に相当する。 12.8 mol% of MnO 2 , SnO 2 , Sb 2 O 3 , and V 2 O 5 are 80.4%, 80.4%, and 120.6%, respectively, when converted to the weight loss rate of tungsten carbide. And 201%.
　実施例１３から１６の重量減少率は、金属酸化物を添加しなかったことを除く実験条件が同一である比較例４（表６）の重量減少率（２．０％）よりも大きかった。なお、Ｖ2Ｏ5を用いた実施例１６は、超硬チップが完全に粉末状に変化したため、重量測定を実施できなかった。実施例１６において、回収した塩中のタングステン濃度をＩＣＰ－ＡＥＳで測定したところ、超硬チップの６２．２％相当のタングステンが溶解していた。つまり、酸化バナジウムは、非常に高い効果を発揮した。 The weight loss rate of Examples 13 to 16 was larger than the weight loss rate (2.0%) of Comparative Example 4 (Table 6) under the same experimental conditions except that no metal oxide was added. In Example 16 using V 2 O 5 , the weight could not be measured because the carbide chips were completely changed to powder. In Example 16, when the tungsten concentration in the recovered salt was measured by ICP-AES, 62.2% of the tungsten in the cemented carbide chip was dissolved. In other words, vanadium oxide exerted a very high effect.
（実施例１７及び１８）
　金属酸化物としてＣｏ3Ｏ4又はＮｉＯを用いたことを除き、実施例７と同じ方法で溶融炭酸塩法による超硬チップの酸化溶解処理を実施した。その後、実施例１と同じ方法で重量減少率を計算した。結果を表１１に示す。 (Examples 17 and 18)
Except for the fact that Co 3 O 4 or Ni O was used as the metal oxide, the cemented carbide chip was oxidatively dissolved by the molten carbonate method in the same manner as in Example 7. Then, the weight loss rate was calculated by the same method as in Example 1. The results are shown in Table 11.
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000011
　実施例１７及び１８の重量減少率は、金属酸化物を添加しなかったことを除く実験条件が同一である比較例４（表６）の重量減少率（２．０％）よりも大きかった。 The weight loss rate of Examples 17 and 18 was larger than the weight loss rate (2.0%) of Comparative Example 4 (Table 6) under the same experimental conditions except that no metal oxide was added.
　本発明は、タングステン含有材料からのタングステンの回収に有用である。 The present invention is useful for recovering tungsten from a tungsten-containing material.

Claims (15)

  1. 　アルカリ金属炭酸塩及びタングステンに対して酸化剤として働く金属イオンを含有する溶融炭酸塩とタングステン含有材料とを接触させることを含む、
    　タングステン酸のアルカリ金属塩の製造方法。     Includes contacting a tungsten-containing material with a molten carbonate containing a metal ion that acts as an oxidant to the alkali metal carbonate and tungsten.
    A method for producing an alkali metal salt of tungstic acid.
  2. 　前記金属イオンは、Ｃｕイオン、Ｆｅイオン、Ｎｉイオン、Ｓｎイオン、Ｍｎイオン、Ｖイオン、Ｐｂイオン、Ｓｂイオン、及びＣｏイオンからなる群より選ばれる少なくとも１つを含む、
    　請求項１に記載のタングステン酸のアルカリ金属塩の製造方法。     The metal ion contains at least one selected from the group consisting of Cu ion, Fe ion, Ni ion, Sn ion, Mn ion, V ion, Pb ion, Sb ion, and Co ion.
    The method for producing an alkali metal salt of tungstic acid according to claim 1.
  3. 　前記金属イオンは、Ｃｕ（＋１）、Ｃｕ（＋２）、Ｆｅ（＋２）、Ｆｅ（＋３）、Ｎｉ（＋２）、Ｓｎ（＋２）、Ｓｎ（＋４）、Ｍｎ（＋２）、Ｍｎ（＋４）、Ｖ（＋２）、Ｖ（＋３）、Ｖ（＋４）、Ｖ（＋５）、Ｐｂ（＋２）、Ｐｂ（＋４）、Ｓｂ（＋３）、Ｓｂ（＋４）、Ｓｂ（＋５）、Ｃｏ（＋２）、及びＣｏ（＋３）からなる群より選ばれる少なくとも１つを含む、
    　請求項１又は２に記載のタングステン酸のアルカリ金属塩の製造方法。     The metal ions include Cu (+1), Cu (+2), Fe (+2), Fe (+3), Ni (+2), Sn (+2), Sn (+4), Mn (+2), Mn (+4), V (+2), V (+3), V (+4), V (+5), Pb (+2), Pb (+4), Sb (+3), Sb (+4), Sb (+5), Co (+2), And at least one selected from the group consisting of Co (+3),
    The method for producing an alkali metal salt of tungstic acid according to claim 1 or 2.
  4. 　前記金属イオンが金属酸化物及び金属炭酸塩からなる群より選ばれる少なくとも１つから供給される、
    　請求項１から３のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法。     The metal ion is supplied from at least one selected from the group consisting of metal oxides and metal carbonates.
    The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 3.
  5. 　前記金属酸化物がＣｕＯ、Ｃｕ2Ｏ、ＶＯ、Ｖ2Ｏ3、ＶＯ2、及びＶ2Ｏ5からなる群より選ばれる少なくとも１つを含む、
    　請求項４に記載のタングステン酸のアルカリ金属塩の製造方法。     The metal oxide comprises at least one selected from the group consisting of CuO, Cu 2 O, VO, V 2 O 3 , VO 2 and V 2 O 5 .
    The method for producing an alkali metal salt of tungstic acid according to claim 4.
  6. 　前記アルカリ金属炭酸塩は、Ｎａ2ＣＯ3、Ｌｉ2ＣＯ3及びＫ2ＣＯ3からなる群より選ばれる少なくとも１つを含む、
    　請求項１から５のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法。     The alkali metal carbonate comprises at least one selected from the group consisting of Na 2 CO 3 , Li 2 CO 3 and K 2 CO 3 .
    The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 5.
  7. 　前記アルカリ金属炭酸塩は、Ｎａ2ＣＯ3を含み、
    　前記アルカリ金属炭酸塩の融液中における前記金属イオンの酸化還元電位は、－０．９４Ｖよりも貴である、
    　請求項６に記載のタングステン酸のアルカリ金属塩の製造方法。     The alkali metal carbonate contains Na 2 CO 3 and contains
    The redox potential of the metal ion in the melt of the alkali metal carbonate is noble than −0.94V.
    The method for producing an alkali metal salt of tungstic acid according to claim 6.
  8. 　前記溶融炭酸塩の温度が５００℃以上１０００℃以下である、
    　請求項１から７のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法。     The temperature of the molten carbonate is 500 ° C. or higher and 1000 ° C. or lower.
    The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 7.
  9. 　前記溶融炭酸塩が接する雰囲気ガスがＣＯ2ガスを含む、
    　請求項１から８のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法。     The atmospheric gas in contact with the molten carbonate contains CO 2 gas.
    The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 8.
  10. 　前記タングステン含有材料が粉末状の炭化タングステンを含む、
    　請求項１から９のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法。     The tungsten-containing material contains powdered tungsten carbide.
    The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 9.
  11. 　請求項１から１０のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法を含む、
    　タングステンの製造方法。     The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 10.
    Tungsten manufacturing method.
  12. 　請求項１から１０のいずれか１項に記載のタングステン酸のアルカリ金属塩の製造方法を含む、
    　パラタングステン酸アンモニウムの製造方法。     The method for producing an alkali metal salt of tungstic acid according to any one of claims 1 to 10.
    A method for producing ammonium paratungstate.
  13. 　アルカリ金属炭酸塩と、
    　タングステン酸のアルカリ金属塩と、
    　タングステンに対して酸化剤として働く金属イオンの還元生成物と、
    　を含む、タングステン酸のアルカリ金属塩を含む組成物。     Alkali metal carbonate and
    Alkali metal salt of tungstic acid and
    Reduction products of metal ions that act as an oxidant for tungsten,
    A composition comprising an alkali metal salt of tungstic acid.
  14. 　タングステン及びコバルトを含み、
    　タングステン濃度に対するコバルト濃度の割合が０．５％以下である、
    　タングステン酸のアルカリ金属塩。     Contains tungsten and cobalt,
    The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less.
    Alkali metal salt of tungstic acid.
  15. 　タングステン及びコバルトを含み、
    　タングステン濃度に対するコバルト濃度の割合が０．５％以下である、
    　パラタングステン酸アンモニウム。
          Contains tungsten and cobalt,
    The ratio of the cobalt concentration to the tungsten concentration is 0.5% or less.
    Ammonium paratungstate.
PCT/JP2021/040440 2020-11-24 2021-11-02 Method for producing alkali metal salt of tungstic acid, method for producing tungsten, and composition containing alkali metal salt of tungstic acid WO2022113669A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11505801A (en) * 1995-06-12 1999-05-25 エイチ・シー・スタルク・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング・ウント・コンパニー・コマンジツトゲゼルシヤフト Manufacturing method of sodium tungstate
JP2010512456A (en) * 2006-12-08 2010-04-22 タンドラ パーティクル テクノロジーズ，リミティド ライアビリティ カンパニー Melting method using alkali metal metalate
WO2010104009A1 (en) * 2009-03-11 2010-09-16 株式会社アライドマテリアル Process for producing sodium tungstate, method for collecting tungsten, apparatus for producing sodium tungstate, and process for producing aqueous sodium tungstate solution
WO2014142003A1 (en) * 2013-03-15 2014-09-18 株式会社アライドマテリアル Sodium tungstate production method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11505801A (en) * 1995-06-12 1999-05-25 エイチ・シー・スタルク・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング・ウント・コンパニー・コマンジツトゲゼルシヤフト Manufacturing method of sodium tungstate
JP2010512456A (en) * 2006-12-08 2010-04-22 タンドラ パーティクル テクノロジーズ，リミティド ライアビリティ カンパニー Melting method using alkali metal metalate
WO2010104009A1 (en) * 2009-03-11 2010-09-16 株式会社アライドマテリアル Process for producing sodium tungstate, method for collecting tungsten, apparatus for producing sodium tungstate, and process for producing aqueous sodium tungstate solution
WO2014142003A1 (en) * 2013-03-15 2014-09-18 株式会社アライドマテリアル Sodium tungstate production method

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