Method for producing metal by molten salt electrolysis and apparatus used for the production method

Abstract

Provided is a method for obtaining a particular metal at high purity, with safety, and at low cost, from a treatment object containing two or more metal elements. The present invention provides a method for producing a metal by molten salt electrolysis, the method including a step of dissolving, in a molten salt, a metal element contained in a treatment object containing two or more metal elements; and a step of depositing or alloying a particular metal present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing the dissolved metal element, by controlling a potential of the electrode members to a predetermined value.

1 . A method for producing a metal by molten salt electrolysis, the method comprising:
 a step of dissolving, in a molten salt, a metal element contained in a treatment object containing two or more metal elements; and   a step of depositing or alloying a particular metal present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing the dissolved metal element, by controlling a potential of the electrode members to a predetermined value.   
     
     
         2 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object is an ore or a crude metal ingot obtained from the ore. 
     
     
         3 . The method for producing a metal by molten salt electrolysis according to  claim 1 ,
 wherein the method is a method for producing tungsten,   a metal element contained in the treatment object is tungsten,   in the step of dissolving, in a molten salt, a metal element from a treatment object, tungsten is dissolved from the treatment object, and   in the step of depositing or alloying a particular metal, tungsten present in the molten salt is deposited on one of a pair of electrode members disposed in the molten salt containing dissolved tungsten, by controlling a potential of the electrode members to a predetermined value.   
     
     
         4 . The method for producing a metal by molten salt electrolysis according to  claim 3 , wherein the treatment object is a metal material containing the tungsten. 
     
     
         5 . The method for producing tungsten a metal by molten salt electrolysis according to  claim 3 , wherein the treatment object is a metal material containing tungsten and a transition metal. 
     
     
         6 . The method for producing a metal by molten salt electrolysis according to  claim 3 , wherein the treatment object is a cemented carbide product. 
     
     
         7 . The method for producing a metal by molten salt electrolysis according to  claim 1 ,
 wherein the method is a method for producing lithium,   a metal element contained in the treatment object is lithium,   in the step of dissolving, in a molten salt, a metal element from a treatment object, lithium is dissolved from the treatment object, and   in the step of depositing or alloying a particular metal, lithium present in the molten salt is deposited on one of a pair of electrode members disposed in the molten salt containing dissolved lithium, by controlling a potential of the electrode members to a predetermined value.   
     
     
         8 . The method for producing a metal by molten salt electrolysis according to  claim 7 , wherein the treatment object is a material containing lithium and a transition metal. 
     
     
         9 . The method for producing a metal by molten salt electrolysis according to  claim 7 , wherein the treatment object is a battery electrode material containing lithium. 
     
     
         10 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object contains a transition metal or a rare earth metal. 
     
     
         11 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object contains one or more metals selected from the group consisting of V, Nb, Mo, Ti, Ta, Zr, and Hf. 
     
     
         12 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object contains Sr and/or Ba. 
     
     
         13 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object contains one or more metals selected from the group consisting of Zn, Cd, Ga, In, Ge, Sn, Pb, Sb, and Bi. 
     
     
         14 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the molten salt is selected such that, in the step of depositing or alloying a particular metal, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more. 
     
     
         15 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein, in the step of depositing or alloying a particular metal, the potential of the electrode members is controlled to the predetermined value so that the particular metal in the molten salt is selectively deposited or alloyed. 
     
     
         16 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein, in the step of dissolving, in a molten salt, a metal element contained in a treatment object,
 the metal element is dissolved in the molten salt by a chemical procedure.   
     
     
         17 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein, in the step of dissolving, in a molten salt, a metal element contained in a treatment object,
 a cathode and an anode that is formed of an anode material containing the treatment object are disposed in the molten salt, and a potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential is dissolved in the molten salt from the treatment object.   
     
     
         18 . The method for producing a metal by molten salt electrolysis according to  claim 17 , wherein the molten salt is selected such that, in the step of dissolving, in a molten salt, a metal element contained in a treatment object, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more. 
     
     
         19 . The method for producing a metal by molten salt electrolysis according to  claim 17 , wherein, in the step of dissolving, in a molten salt, a metal element contained in a treatment object, the potential at the anode is controlled to a predetermined value so that the particular metal element is selectively dissolved in the molten salt. 
     
     
         20 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein, in the step of dissolving, in a molten salt, a metal element contained in a treatment object, one or more metals each serving as the particular metal are dissolved in the molten salt. 
     
     
         21 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the particular metal deposited or alloyed is a transition metal. 
     
     
         22 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the particular metal deposited or alloyed is a rare earth metal. 
     
     
         23 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the particular metal deposited or alloyed is V, Nb, Mo, Ti, Ta, Zr, or Hf. 
     
     
         24 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the particular metal deposited or alloyed is Sr or Ba. 
     
     
         25 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the particular metal deposited or alloyed is Zn, Cd, Ga, In, Ge, Sn, Pb, Sb, or Bi. 
     
     
         26 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the molten salt is a chloride or fluoride molten salt. 
     
     
         27 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the molten salt is a molten salt mixture containing a chloride molten salt and a fluoride molten salt. 
     
     
         28 . The method for producing a metal by molten salt electrolysis according to  claim 1 , wherein the treatment object has a form of particles or powder. 
     
     
         29 . The method for producing a metal by molten salt electrolysis according to  claim 28 , wherein the treatment object having the form of particles or powder is compacted to form the anode. 
     
     
         30 . A method for producing a metal by molten salt electrolysis, the method being a method for producing a particular metal by molten salt electrolysis from a treatment object containing two or more metal elements,
 wherein a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and a potential at the anode is controlled to a predetermined value so that a particular metal is left in the anode by performing a step of dissolving a metal element corresponding to the controlled potential in the molten salt from the treatment object.   
     
     
         31 . The method for producing a metal by molten salt electrolysis according to  claim 30 , wherein the treatment object is an ore or a crude metal ingot obtained from the ore. 
     
     
         32 . The method for producing a metal by molten salt electrolysis according to  claim 30 , wherein the method is a method for producing tungsten by molten salt electrolysis from a treatment object containing tungsten,
 a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and a potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential is dissolved in the molten salt from the treatment object and tungsten is left in the anode.   
     
     
         33 . The method for producing a metal by molten salt electrolysis according to  claim 30 , wherein the molten salt is selected such that, in the step of dissolving a metal element in the molten salt from the treatment object, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more. 
     
     
         34 . An apparatus used for a method for producing a metal by molten salt electrolysis, the apparatus comprising:
 a container containing a molten salt;   a cathode immersed in the molten salt contained within the container; and   an anode that is immersed in the molten salt contained within the container and that contains a treatment object containing two or more metal elements,   wherein the molten salt is movable into and out of the anode,   the apparatus further comprises a control unit configured to control a potential of the cathode and the anode to a predetermined value, and   a value of the potential is changeable in the control unit.   
     
     
         35 . An apparatus used for a method for producing a metal by molten salt electrolysis, the apparatus comprising:
 a container containing a molten salt containing two or more dissolved metal elements; a cathode and an anode that are immersed in the molten salt contained within the container; and a control unit configured to control a potential of the cathode and the anode to a predetermined value,   wherein a value of the potential is changeable in the control unit.   
     
     
         36 . The apparatus according to  claim 34 , wherein the two or more metal elements include at least one of tungsten and lithium. 
     
     
         37 . The apparatus according to  claim 35 , wherein the two or more metal elements include at least one of tungsten and lithium.