CN115305521A - Method for preparing metal niobium by molten salt electrolysis - Google Patents
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Abstract
The invention relates to a method for preparing metal niobium by molten salt electrolysis, which comprises the following steps: taking an electrolytic cell comprising an anodic electrolytic chamber and a cathodic electrolytic chamber, and placing a liquid niobium alloy at the bottom of the electrolytic cell for separating the anodic electrolytic chamber and the cathodic electrolytic chamber; adding molten salt a to the anode electrolysis chamber and adding molten salt b to the cathode electrolysis chamber; adding niobium pentoxide into the anode electrolysis chamber, respectively placing the anode and cathode into the anode electrolysis chamber and cathode electrolysis chamber, and electrifying to operate the electrolysis cell to separate out CO and CO at the anode 2 Gas, cathode deposition solid metallic niobium. According to the method for preparing the metal niobium by molten salt electrolysis, the raw material is niobium pentoxide, the requirement on the purity of the raw material is not high, the high-purity metal niobium can be directly obtained, and other impurities are trapped in the liquid niobium alloy and the molten salt; the process flow is simple, efficient and energy-saving, and the operation is continuous.
Description
Technical Field
The invention belongs to the field of niobium metallurgy, and particularly relates to a method for preparing metal niobium through molten salt electrolysis.
Background
Niobium is an important rare metal and has the advantages of high melting point, low steam pressure, good cold processing performance, high chemical stability, strong acid and alkali corrosion resistance and the like. The metal niobium and the alloy thereof are important functional materials and are widely applied to industries such as military industry, national defense, aerospace, special materials, metallurgy, energy and the like.
Niobium metal preparation processes are classified into the following two types, one being a method that has been industrially applied at present: a niobium oxide carbothermic reduction method, a niobium oxide aluminothermic reduction method, a potassium sodium fluoroniobate thermal reduction method, and a niobium oxide molten salt electrolysis method; the other is still in the laboratory research stage at present, and comprises a niobium oxide solid state electric deoxidation method, a niobium oxide calcium thermal reduction method and a niobium oxide solid state oxygen permeable membrane method.
The carbothermic reduction of niobium oxide is a process of reducing niobium pentoxide to metallic niobium with carbon under high temperature vacuum conditions, the reduction process being: nb 2 O 5 +7C＝2NbC+5CO；Nb 2 O 5 +12NbC＝7Nb 2 C+5CO；Nb 2 O 5 +5Nb 2 C =12Nb +5CO. The production process is characterized by intermittent production, low mechanization degree and high content of impurities C and O in metal.
The aluminothermic reduction process of niobium oxide is a process of reducing niobium pentoxide to metallic niobium with metallic aluminum under high temperature vacuum conditions, the reduction process being: 3Nb 2 O 5 +10Al＝6Nb+5Al 2 O 3 . The production process has the same problems of the carbothermic method, such as incapability of continuous operation, low mechanization degree and high content of impurity elements in metal.
The basic principle of the potassium fluoroniobate sodium thermal reduction method is to prepare metal niobium by reducing niobium compounds by utilizing active metals such as alkali metals, alkaline earth metals and the like. For example, U.S. Pat. No. 6,3012877 discloses a method for thermal reduction of potassium fluoroniobate by using a sodium metal molten salt, the chemical process is K 2 NbF 7 +5Na = Nb +2KF +5NaF; chinese patent CN1169643C discloses a method for preparing ultrafine niobium powder by reducing niobium oxide with alkali metal in halide molten salt of alkali metal and alkaline earth metal, the chemical process is as follows: nb 2 O 5 +5CaCl 2 +10Na =2Nb +10NaCl +5CaO. Inert salts (such as halides of KCl, naCl, KF, naF and the like) are required to be added as a diluent in the process of preparing the niobium metal powder. However, the process has the defects of large demand of inert salts, incapability of recycling, incapability of continuous production and the like.
In addition, U.S. Pat. No. 6,36062 discloses a method for preparing niobium metal powder and tantalum powder by reducing tantalum oxide and niobium oxide with magnesium metal, which comprises two reduction processes, the first stage (5-2 x) is Mg + Nb 2 O 5 ＝(5-2x)MgO+2NbO x (x =0.5 to 1.5); second stage, nbO x (x＝0.5 to 1.5) + xMg = Nb + xMgO. The disadvantages of this method are: the niobium metal has high content of impurities Mg and O, the process is complex, and continuous production cannot be realized.
The traditional niobium oxide molten salt electrolysis method adopts potassium fluoroniobate-potassium chloride-sodium chloride mixed molten salt as electrolyte, the raw material niobium pentoxide is added into the electrolyte and subjected to dissolution reaction, niobium ions are reduced on a nickel cathode to prepare metal niobium, and oxygen ions are discharged on a graphite anode to separate out CO and CO 2 . However, the method has the defects that the purity requirement of the required niobium oxide raw material is high, and the content of impurity elements in the metal niobium product is high.
The core of the solid-state electro-deoxidation method for niobium oxide is that solid-state niobium oxide is taken as a cathode, calcium chloride molten salt is taken as electrolyte, and niobium ions in the cathode are reduced into metal niobium in situ through molten salt electrolysis. During reduction, oxygen anions are separated from the cathode, enter the melt, migrate to the anode under the action of an electric field, and are oxidized into oxygen to be separated out (when a carbon anode is adopted, oxygen and carbon further react to generate CO and CO 2). However, the cathode niobium oxide compact is gradually reduced from outside to inside, oxygen diffusion and desorption are increasingly difficult, niobium with low oxygen content is difficult to obtain, and the product purity is limited by the impurity purity in the raw materials.
The core of the niobium oxide solid oxygen permeable membrane method is that solid niobium oxide is used as a cathode, carbon saturated copper liquid in an yttria-stabilized zirconia tube is used as an anode, magnesium oxide-magnesium fluoride mixed molten salt is used as electrolyte, and niobium ions in the cathode are reduced into metal niobium in situ through molten salt electrolysis. During reduction, oxygen anions are separated from the cathode and enter the melt, and are diffused and transferred to the anode through the solid oxygen permeable membrane under the action of an electric field to be oxidized into oxygen to be separated out (when a carbon anode is adopted, oxygen and carbon further react to generate CO and CO 2). The method avoids the problems of side reaction and high impurity content in metal, but the method has the defects of short service life of the solid oxygen permeable membrane, high manufacturing cost and the like, so that the method is difficult to apply on a large scale.
The niobium pentoxide is reduced by a niobium oxide calcium thermal reduction method in stages, and calcium chloride-calcium oxide mixed molten salt is used as electrolyte. Through molten salt electrolysis, oxygen ions discharge on a graphite anode to separate out CO and CO2, and calcium ions are onThe cathode net is reduced to generate liquid metal calcium; the liquid calcium metal then reduces the particulate niobium pentoxide in the cathode mesh to metallic niobium. The reaction process is as follows: nb2O5+5Ca=2Nb +5CaO,
however, the method has the disadvantage that the impurity elements O and C contained in the product metal niobium are high.
Therefore, the technical scheme of the invention is provided.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for preparing metal niobium by molten salt electrolysis. According to the method for preparing the metal niobium by electrolyzing the molten salt, the niobium pentoxide is used as the raw material, the requirement on the purity of the raw material is not high, the high-purity metal niobium can be directly obtained, and other impurities are retained in the liquid niobium alloy and the molten salt; the process flow is simple, efficient and energy-saving, and the operation is continuous.
The scheme of the invention is to provide a method for preparing metal niobium by molten salt electrolysis, which comprises the following steps:
(1) Taking an electrolytic tank containing an anode electrolytic chamber and a cathode electrolytic chamber, and placing a liquid niobium alloy at the bottom of the electrolytic tank for separating the anode electrolytic chamber and the cathode electrolytic chamber;
(2) Adding molten salt a to the anode electrolysis chamber and adding molten salt b to the cathode electrolysis chamber;
(3) Adding niobium pentoxide into the anode electrolysis chamber, respectively placing the anode and cathode into the anode electrolysis chamber and cathode electrolysis chamber, and electrifying to operate the electrolytic cell to separate out CO and CO at the anode 2 Gas, cathode deposition solid metallic niobium.
The temperature control mode comprises the thermal effect of current, heating of a heating element, cooling of a water-cooling sleeve and the like.
Preferably, in the step (1), the liquid niobium alloy is composed of niobium and one or more of gold, palladium, rhodium, nickel, iron, cobalt, gallium, indium and germanium.
In the step (2), the molten salt a is divided into two types, wherein the first type of molten salt a is composed of one or more of calcium chloride, barium chloride, strontium chloride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride and lanthanum chloride.
When the first type of molten salt a is used, the electrolysis principle is as follows:
the electrolytic bath is electrified to operate, the niobium pentoxide raw material is added to the liquid level of the liquid niobium alloy in the anode electrolysis chamber and is insoluble in the molten salt in the anode electrolysis chamber, and niobium ions in the niobium pentoxide raw material are reduced into metal niobium by in-situ electro-deoxidation and are dissolved in the liquid niobium alloy; the oxygen ions combined with niobium move to the surface of the anode under the action of an electric field and are oxidized into zero-valent oxygen, and then the oxygen ions react with anode carbon to generate CO and CO 2 And escape. Meanwhile, niobium atoms in the liquid niobium alloy lose electrons at the interface of the liquid niobium alloy and are oxidized into niobium ions which enter the cathode chamber molten salt, and the niobium ions in the cathode chamber molten salt move to the surface of the cathode under the action of an electric field and are reduced to obtain solid metal niobium.
The second type of fused salt a is composed of one of potassium fluoroniobate and sodium fluoroniobate, and one or more of potassium chloride, potassium fluoride, sodium chloride, sodium fluoride, lithium chloride, lithium fluoride, calcium chloride and calcium fluoride.
When the second type of molten salt a is used, the electrolysis principle is as follows:
the electrolytic cell is electrified to operate, the niobium pentoxide raw material is added into the anode electrolysis chamber and dissolved in the molten salt of the anode electrolysis chamber, and niobium ions in the molten salt move to the interface of the liquid niobium alloy under the action of an electric field to be reduced into metal niobium and dissolved in the liquid niobium alloy; oxygen ions move to the surface of the anode under the action of an electric field and are oxidized into zero-valent oxygen, and then the oxygen ions react with anode carbon to generate CO and CO 2 And escape. Meanwhile, niobium atoms in the liquid niobium alloy lose electrons at the interface of the liquid niobium alloy and are oxidized into niobium ions to enter cathode chamber molten salt, and the niobium ions in the cathode chamber molten salt move to the surface of a cathode under the action of an electric field and are reduced to obtain solid metal niobium.
Preferably, in the step (2), the molten salt b is composed of one of potassium fluoroniobate and sodium fluoroniobate, and one or more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, barium chloride, lithium fluoride, sodium fluoride and potassium fluoride.
Preferably, in step (3), the purity of the niobium pentoxide is ≧ 80% wt.
Preferably, in step (3), the anode is a graphite anode.
Preferably, in step (3), the cathode is a niobium cathode, a tungsten cathode or a molybdenum cathode.
Preferably, in step (3), the temperature at which the cell is operated in step (3) is 700 to 1600 ℃.
Preferably, in the step (3), the current density of the anode for the electrification and electrolysis is 0.01-2.0A/cm 2 。
The invention has the beneficial effects that:
according to the method for preparing the metal niobium by electrolyzing the molten salt, the niobium pentoxide is used as the raw material, the requirement on the purity of the raw material is not high, the high-purity metal niobium can be directly obtained, and other impurities are retained in the liquid niobium alloy and the molten salt; the process flow is simple, efficient and energy-saving, and the operation is continuous.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic view of an electrolytic cell according to the present invention.
Reference numbers in the figures:
1-an anode; 2-molten salt a; 3-niobium pentoxide; 4-liquid niobium alloy; 5-molten salt b; 6-niobium as a cathode product; 7-a cathode; 8-water-cooling sleeve; 9-heat insulation material; 10-a heating element; 11-refractory material; i-an anodic electrolysis chamber; II-cathodic electrolysis chamber.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Example 1
The embodiment provides a method for preparing metallic niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously filled with a niobium-gold alloy (8% by weight niobium, 92% by weight gold), evacuated, and then purged with argon as an inert gas, and the flow rate was maintained at 10mL/min after the cell was filled with argon for argon protection. The cell was then heated to 1300 c and held for 1 hour to completely melt the niobium-gold alloy in the cell, and the resulting liquid niobium alloy partitioned the cell into an anodic chamber and a cathodic chamber.
(2) With (10 at%) LiCl- (40 at%) NaCl-CaCl 2 (50 at%) molten salt as electrolyte of anode chamber of electrolytic cell, na 2 NbF 7 (22 wt%) -NaCl (40 wt%) -KCl (38 wt%) molten salt as the electrolyzer catholyte; niobium pentoxide raw material (80% purity by weight) was added to the liquid niobium alloy interface in the anode cell, followed by controlling the cell anode cell molten salt temperature at 750 ℃, the cell cathode cell molten salt temperature at 750 ℃, the cell bottom liquid niobium alloy temperature at 1300 ℃, and the insertion of graphite anodes into the anode cell electrolyte and niobium cathodes into the cathode cell molten salt as the cell compartment temperatures stabilized. Electrifying for electrolysis for 12h, and controlling the current density of the anode to be 0.01A/cm 2 And preparing a cathode product, namely metallic niobium in a cathode electrolytic chamber (the purity of the niobium is detected to be 99.95%).
Example 2
The embodiment provides a method for preparing metal niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously filled with niobium-indium alloy (15% by weight niobium, 85% by weight indium), evacuated, and then purged with argon as an inert gas, and after the cell was filled with argon, the flow rate was maintained at 20mL/min for continuous argon protection. The cell was then heated to 740 ℃ and held for 2 hours to completely melt the niobium indium alloy in the cell and the resulting liquid niobium alloy partitioned the cell into an anodic cell and a cathodic cell.
(2) With K 2 NbF 7 (17.5% wt) -KF (27.5% wt) -KCl (50.0% wt) -LiCl (5% wt) molten salt is the electrolyzer anolyte, K 2 NbF 7 (22 wt%) -NaCl (40 wt%) -KCl (38 wt%) molten salt as the electrolyzer catholyte; and then controlling the temperature of the molten salt in the anode electrolysis chamber of the electrolysis bath at 740 ℃, controlling the temperature of the molten salt in the cathode electrolysis chamber of the electrolysis bath at 740 ℃, controlling the temperature of the liquid niobium alloy at the bottom of the electrolysis bath at 740 ℃, inserting the graphite anode into the electrolyte in the anode electrolysis chamber and inserting the niobium cathode into the molten salt in the cathode electrolysis chamber when the temperature of each subarea of the electrolysis bath is stable. The raw material niobium pentoxide (purity: 80 wt%) was added to the anode cell in an amount of 1.5% of the total mass of the molten salt in the anode cell, and subjected to electrolysis for 12 hours while controlling the anode current density to 0.05A/cm 2 And preparing a cathode product, namely metallic niobium in a cathode electrolytic chamber (the purity of the niobium is detected to be 99.96%).
Example 3
The embodiment provides a method for preparing metal niobium by molten salt electrolysis, which comprises the following steps:
(1) The cell bottom was pre-alloyed with ferrocolumbium (74% by weight niobium, 26% by weight iron), evacuated and then purged with argon as an inert gas, and kept at a flow rate of 30mL/min for argon protection after argon filling. And then heating the electrolytic cell to 1500 ℃, and preserving the heat for 1 hour to ensure that the niobium-iron alloy in the electrolytic cell is completely melted, and the formed liquid niobium alloy divides the electrolytic cell into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With (46.7 at%) NaCl-CaCl 2 (53.3 at%) molten salt as electrolyte in the anode chamber of the cell, K 2 NbF 7 (40% by weight) -NaCl (40% by weight) -KCl (20% by weight) molten salt as the cell catholyte; adding niobium pentoxide raw material (purity 85%) to liquid niobium alloy interface of anode electrolytic chamber, and then anodizing the electrolytic cellThe temperature of the electrolytic cell is controlled at 750 ℃, the temperature of the electrolytic cell cathode electrolytic cell is controlled at 750 ℃, the temperature of the liquid niobium alloy at the bottom of the electrolytic cell is controlled at 1500 ℃, after the temperature of each subarea of the electrolytic cell is stable, the graphite anode is inserted into the anode electrolytic cell molten salt, and the tungsten cathode is inserted into the cathode electrolytic cell molten salt. Electrifying for electrolysis for 12h, and controlling the current density of the anode to be 0.5A/cm 2 And preparing a cathode product, namely metallic niobium in a cathode electrolytic chamber (the purity of the niobium is detected to be 99.95%).
Example 4
The embodiment provides a method for preparing metallic niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously placed with niobium cobalt alloy (25% by weight niobium, 75% by weight cobalt), the cell was evacuated and then purged with argon as an inert gas, and after the cell was filled with argon, a flow of 40mL/min was maintained for continuous argon shielding. And then heating the electrolytic cell to 1300 ℃, and keeping the temperature for 1 hour to ensure that the niobium-cobalt alloy in the electrolytic cell is completely melted, and the formed liquid niobium alloy divides the electrolytic cell into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With Na 2 NbF 7 (17.5% wt) -KF (27.5% wt) -KCl (55.0% wt) molten salt as the electrolyzer anolyte, K 2 NbF 7 (40% wt) -NaCl (40% wt) -KCl (20% wt) molten salt as the electrolyzer cathode electrolyte. And then controlling the temperature of molten salt in an anode electrolysis chamber of the electrolysis cell at 750 ℃, controlling the temperature of molten salt in a cathode electrolysis chamber of the electrolysis cell at 750 ℃, controlling the temperature of liquid niobium alloy at the bottom of the electrolysis cell at 1300 ℃, inserting a graphite anode into the molten salt in the anode electrolysis chamber and inserting a molybdenum cathode into the molten salt in the cathode electrolysis chamber after the temperatures of all the subareas of the electrolysis cell are stable. Adding niobium pentoxide (with purity of 97 wt%) into the anode electrolytic chamber at 1.6% of the total molten salt mass, electrolyzing for 20h, and controlling anode current density at 2.0A/cm 2 And preparing cathode product metal niobium (the purity of the niobium is 99.95 percent through detection) in a cathode electrolytic chamber.
Example 5
The embodiment provides a method for preparing metallic niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously placed with niobium palladium alloy (50% by weight niobium, 50% by weight palladium), the cell was evacuated and then purged with argon as an inert gas, and after the cell was filled with argon, a flow of 35mL/min was maintained for continuous argon shielding. And then heating the electrolytic cell to 1600 ℃, and preserving the heat for 2 hours to ensure that the niobium-palladium alloy in the electrolytic cell is completely melted, and the formed liquid niobium alloy divides the electrolytic cell into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With (46.7 at%) NaCl-CaCl 2 (53.3 at%) molten salt as electrolyte in the anode chamber of the cell, K 2 NbF 7 (40% by weight) -NaCl (40% by weight) -KCl (20% by weight) molten salt as the cell catholyte; niobium pentoxide raw material (purity: 88% by weight) was added to the liquid niobium alloy interface in the anode cell, followed by cell anode cell temperature control at 750 ℃, cell cathode cell temperature control at 750 ℃, cell bottom liquid niobium alloy temperature control at 1600 ℃, and after cell partition temperature stabilization, graphite anodes were inserted into the anode cell molten salt and niobium cathodes were inserted into the cathode cell molten salt. Electrifying and electrolyzing for 12h, and controlling the current density of the anode to be 0.8A/cm 2 And preparing a cathode product, namely metallic niobium in a cathode electrolytic chamber (the purity of the niobium is detected to be 99.95%).
Example 6
The embodiment provides a method for preparing metallic niobium by molten salt electrolysis, which comprises the following steps:
(1) Placing niobium-germanium alloy (10% by weight niobium, 90% by weight germanium) in advance at the bottom of the electrolytic cell, evacuating the electrolytic cell and then passing inert gas argon, maintaining a flow of 20mL/min for continuous argon protection after argon filling. And then heating the electrolytic bath to 1400 ℃, and preserving the heat for 2 hours to ensure that the niobium-germanium alloy in the electrolytic bath is completely melted, and the formed liquid niobium alloy divides the electrolytic bath into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With K 2 NbF 7 (17.5% wt) -KF (27.5% wt) -KCl (55.0% wt) molten salt as the electrolyzer anolyte compartment electrolyte K 2 NbF 7 (22 wt%) -NaCl (40 wt%) -KCl (38 wt%) molten salt was used as the electrolyzer catholyte. Then controlling the molten salt temperature of an anode electrolysis chamber of the electrolysis bath at 750 ℃, controlling the molten salt temperature of a cathode electrolysis chamber of the electrolysis bath at 750 ℃, and controlling the liquid niobium at the bottom of the electrolysis bathControlling the alloy temperature at 1400 ℃, inserting the graphite anode into the anode electrolysis chamber molten salt and inserting the niobium cathode into the cathode electrolysis chamber molten salt after the temperature of each subarea of the electrolysis bath is stable. Adding raw material niobium pentoxide (with purity of 95 wt%) into the anode electrolytic chamber at 2% of the total molten salt mass, electrolyzing for 24h, and controlling anode current density at 1.5A/cm 2 And preparing cathode product metal niobium (the purity of the niobium is 99.96 percent through detection) in a cathode electrolytic chamber.
Example 7
The embodiment provides a method for preparing metallic niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously provided with a niobium rhodium alloy (55% by weight niobium, 45% by weight rhodium), the cell was evacuated and then purged with argon as an inert gas, and after the cell was filled with argon, a flow rate of 50mL/min was maintained for continuous argon shielding. And then heating the electrolytic cell to 1600 ℃, and preserving the heat for 2 hours to ensure that the niobium-rhodium alloy in the electrolytic cell is completely melted, and the formed liquid niobium alloy divides the electrolytic cell into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With K 2 NbF 7 (40% by weight) -NaCl (40% by weight) -KCl (20% by weight) molten salt as the cell anolyte, K 2 NbF 7 (22 wt%) -NaCl (40 wt%) -KCl (38 wt%) molten salt was used as the electrolyzer catholyte. And then controlling the temperature of molten salt in an anode electrolysis chamber of the electrolysis cell to be 700 ℃, controlling the temperature of molten salt in a cathode electrolysis chamber of the electrolysis cell to be 700 ℃, controlling the temperature of liquid niobium alloy at the bottom of the electrolysis cell to be 1600 ℃, inserting a graphite anode into the molten salt in the anode electrolysis chamber and inserting a niobium cathode into the molten salt in the cathode electrolysis chamber after the temperatures of all the subareas of the electrolysis cell are stable. The raw material niobium pentoxide (purity: 90 wt%) was added to the anode chamber in an amount of 1.5% of the total mass of the molten salt in the anode chamber, and electrolysis was conducted for 20 hours while controlling the anode current density at 0.05A/cm 2 And preparing cathode product metal niobium (the purity of the niobium is 99.96 percent through detection) in a cathode electrolytic chamber.
Example 8
The embodiment provides a method for preparing metal niobium by molten salt electrolysis, which comprises the following steps:
(1) The bottom of the cell was previously placed with niobium-nickel alloy (50% by weight niobium, 50% by weight nickel), the cell was evacuated and then purged with argon as an inert gas, and after the cell was filled with argon, a flow of 10mL/min was maintained for continuous argon shielding. And then heating the electrolytic cell to 1400 ℃, and keeping the temperature for 1.5 hours to completely melt the niobium-nickel alloy in the electrolytic cell, wherein the formed liquid niobium alloy divides the electrolytic cell into an anode electrolytic chamber and a cathode electrolytic chamber.
(2) With CaCl 2 (95% by weight) -CaO (5%) molten salt as the electrolyzer anolyte, K 2 NbF 7 (40% wt) -NaCl (40% wt) -KCl (20% wt) molten salt as the cell catholyte. Niobium pentoxide raw material (purity 92% wt) was added to the liquid niobium alloy interface in the anode cell, followed by controlling the cell anode cell molten salt temperature at 800 ℃, the cell cathode cell molten salt temperature at 800 ℃, the cell bottom liquid niobium alloy temperature at 1400 ℃, and after the cell compartment temperatures stabilized, the graphite anodes were inserted into the anode cell molten salt and the niobium cathodes were inserted into the cathode cell molten salt. Electrifying for electrolysis for 20h, and controlling the current density of the anode to be 1.2A/cm 2 And preparing a cathode product, namely metallic niobium in a cathode electrolytic chamber (the purity of the niobium is detected to be 99.96%).
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for preparing metal niobium by molten salt electrolysis is characterized by comprising the following steps:
(1) Taking an electrolytic tank containing an anode electrolytic chamber and a cathode electrolytic chamber, and placing a liquid niobium alloy at the bottom of the electrolytic tank for separating the anode electrolytic chamber and the cathode electrolytic chamber;
(2) Adding a molten salt a to the anode electrolysis chamber and adding a molten salt b to the cathode electrolysis chamber;
(3) Adding the raw material niobium pentoxide into the anode for electrolysisPlacing the anode and cathode in anode electrolysis chamber and cathode electrolysis chamber respectively, then electrifying to operate the electrolytic cell, and separating CO and CO out of the anode 2 Gas, cathode to deposit solid metallic niobium.
2. The method for preparing metallic niobium by molten salt electrolysis as claimed in claim 1, wherein in step (1), the liquid niobium alloy is composed of niobium and one or more of gold, palladium, rhodium, nickel, iron, cobalt, gallium, indium and germanium.
3. The method for preparing metallic niobium by molten salt electrolysis according to claim 1, wherein in the step (2), the molten salt a is composed of one or more of calcium chloride, barium chloride, strontium chloride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride and lanthanum chloride.
4. The method for preparing metallic niobium by molten salt electrolysis as claimed in claim 1, wherein in the step (2), the molten salt a is composed of one of potassium fluoroniobate and sodium fluoroniobate, and one or more of potassium chloride, potassium fluoride, sodium chloride, sodium fluoride, lithium chloride, lithium fluoride, calcium chloride and calcium fluoride.
5. The method for preparing metallic niobium by molten salt electrolysis as claimed in claim 1, wherein in the step (2), the molten salt b is composed of one of potassium fluoroniobate and sodium fluoroniobate, and one or more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, barium chloride, lithium fluoride, sodium fluoride and potassium fluoride.
6. The molten salt electrolysis process for preparing metallic niobium according to claim 1, wherein in step (3), the purity of niobium pentoxide is ≥ 80% wt.
7. The method for preparing metallic niobium by molten salt electrolysis as claimed in claim 1, wherein in step (3), the anode is a graphite anode.
8. The method for producing metallic niobium by molten salt electrolysis according to claim 1, wherein in the step (3), the cathode is a niobium cathode, a tungsten cathode or a molybdenum cathode.
9. The method for producing metallic niobium by molten salt electrolysis as claimed in claim 1, wherein the temperature at which the electrolytic cell is operated in step (3) is 700 to 1600 ℃.
10. The molten salt electrolysis process for preparing metallic niobium according to claim 1, wherein in the step (3), the current density of the anode for the electrolysis is 0.01-2.0A/cm 2 。
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