ELECTROCHEMICAL METHOD FOR SEPARATION OF ZIRCONIUM AND HAFNIUM

Abstract

The present disclosure provides an electrochemical method for the separation of zirconium and hafnium, using an electrolytic cell equipped with an anode chamber and a cathode chamber, wherein the anode chamber and the cathode chamber are separated by a liquid alloy. In particular, the liquid alloy comprises a crude zirconium and a matrix metal with the metal activity lower than zirconium. After the electrolysis reaction is started, since the metal activity series in the liquid alloy is: hafnium>zirconium>>matrix metal, the hafnium in the liquid alloy is oxidized prior to the zirconium, the hafnium in ionic form migrates into the cathode electrolyte in the cathode chamber, leading to a continuous decrease of hafnium content in the liquid alloy, whereas the zirconium remains in the liquid alloy. Accordingly, deep separation of zirconium from hafnium is achieved, and therefore, nuclear-grade zirconium products can be prepared.

Claims

1. An electrochemical method for the separation of zirconium and hafnium, the method comprises: An electrolytic cell equipped with an anode chamber and a cathode chamber is used, wherein there is an anode electrolyte in the anode chamber and there is a cathode electrolyte in the cathode chamber, an anode is inserted into the anode electrolyte, a cathode is inserted into the cathode electrolyte: the anode chamber and the cathode chamber are separated by a liquid alloy, and both the anode and the cathode are not in contact with the liquid alloy; the liquid alloy comprises solute metal and matrix metal, the solute metal is crude zirconium, the crude zirconium contains hafnium element: the metal activity of the matrix metal is lower than the metal activity of zirconium; applying electrical current for electrolysis, the hafnium content in the liquid alloy continuously decreases, whereas the zirconium remains in the liquid alloy, therefore the separation of zirconium from hafnium is achieved.

2. An electrochemical method for the separation of zirconium and hafnium according to claim 1, the material of the anode is selected from one of graphite, copper, and zirconium.

3. An electrochemical method for the separation of zirconium and hafnium according to claim 2, when the material of the anode is graphite, a zirconium-containing material is added into the anode chamber, the zirconium-containing material is a halide of zirconium or an oxide of zirconium.

4. An electrochemical method for the separation of zirconium and hafnium according to claim 3, the zirconium-containing material is selected from one or several of Na.sub.2ZrCl.sub.6, K.sub.2ZrCl.sub.6, Na.sub.2ZrF.sub.6, K.sub.2ZrF.sub.6, ZrO.sub.2, ZrCl.sub.2, ZrCl.sub.3, ZrCl.sub.4.

5. An electrochemical method for the separation of zirconium and hafnium according to claim 2, when the material of the anode is copper or crude zirconium, there is no need to add a zirconium-containing material into the anode chamber.

6. An electrochemical method for the separation of zirconium and hafnium according to claim 1, the matrix metal is selected from one or several of copper, lead, zinc, tin, bismuth, and the melting point of the liquid alloy formed by the solute metal and the matrix metal is lower than 1100? C.

7. An electrochemical method for the separation of zirconium and hafnium according to claim 2, when the material of the anode is copper, the anode electrolyte is selected from one or several of CuCl.sub.2 and LiF, NaF, KF, LiCl, NaCl, KCl, CaCl.sub.2; when the material of the anode is graphite or zirconium, the anode electrolyte is selected from one or several of ZrCl.sub.4, ZrCl.sub.2, ZrCl.sub.3, Na.sub.2ZrF.sub.6, K.sub.2ZrF.sub.6 or one or several of LiF, NaF, KF, LiCl, NaCl, KCl, CaCl.sub.2; the cathode electrolyte is selected from one or several of LiF, NaF, KF, LiCl, NaCl, KCl, CuCl.sub.2, there are a zirconium halide and/or a hafnium halide dissolved in the cathode electrolyte, and the zirconium halide and/or the hafnium halide are selected from one or several of ZrCl.sub.4, ZrCl.sub.2, ZrCl.sub.3, HfCl.sub.4, HfCl.sub.2, HfCl.sub.3, Na.sub.2ZrCl.sub.6, K.sub.2ZrCl.sub.6, Na.sub.2HfCl.sub.6, K.sub.2HfCl.sub.6, Na.sub.2ZrF.sub.6, K.sub.2ZrF.sub.6, Na.sub.2HfF.sub.6, K.sub.2HfF.sub.6.

8. An electrochemical method for the separation of zirconium and hafnium according to claim 7, the zirconium halide and/or the hafnium halide are dissolved in the cathode electrolyte.

9. An electrochemical method for the separation of zirconium and hafnium according to claim 1, the material of the cathode is stainless steel, zirconium, titanium or tungsten.

10. An electrochemical method for the separation of zirconium and hafnium according to claim 1, the electrolysis reaction is carried out under the protection of the argon gas, the electrolysis reaction temperature is 400-1100? C., the anode current density is controlled at 0.002-0.5 A.Math.cm.sup.?2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic structural diagram of the electrolytic cell of the present disclosure.

[0024] Where, 1anode; 2anode chamber; 3liquid alloy; 4cathode chamber; 5cathode; 6cell body; 7resistance wire; 8air inlet; 9air outlet; 10zirconium-containing material feed port; 11liquid alloy feed port.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To make the purpose, technical solutions and advantages of the present disclosure clearer, the technical solutions of the present disclosure will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, but are not all of the embodiments. Based on the embodiments in the present disclosure, all other implementations obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present disclosure.

[0026] The embodiments of the present disclosure relate to an electrochemical method for separating zirconium and hafnium, and the method is carried out in an electrolytic cell. As shown in FIG. 1, the main body of the electrolytic cell used in the present disclosure is the cell body 6, the electrolytic cell has an anode chamber 2 and a cathode chamber 4, wherein there are an anode electrolyte and an anode 1 in the anode chamber 2, there are a cathode electrolyte and a cathode 5 in the cathode chamber 4, the anode chamber 2 and the cathode chamber 4 are separated by a liquid alloy 3. In FIG. 1, there is a connected section at lower body of the inside of the cell body 6 and the liquid alloy 3 is filled in the connected section, the anode chamber 2 and the cathode chamber 4 are respectively at the upper body of the inside of the cell body 6. The interface formed by the liquid alloy 3 and the electrolyte defines the regions of the anode chamber 2 and the cathode chamber 4, and both cathode 5 and the anode 1 are not in contact with the liquid alloy 3.

[0027] The cell body 6 is an enclosed structure in overall view, there is an air inlet 8 at the top of the cell body 6 for the entry of inert gas, and there is an air outlet 9 at the top of the cell body 6 for the discharge of gases from within the cell body 6. There is a zirconium-containing material feed port 10 at the top of the anode chamber, and there is a liquid alloy feed port 11 between the anode chamber 2 and the cathode chamber 4. There is a resistance wire on the outer surface of the cell body 6 for heating.

[0028] After the electrolysis is carried out for a certain period of time, the liquid alloy can be directly subjected to electrolytic separation, and the solute metal zirconium and the matrix metal in the liquid alloy are separated by electrolysis, achieving the extraction of zirconium from the liquid alloy; or after the cooling of the electrolysis reaction system, the metal phase and electrolyte are separated, and then the extraction from the liquid alloy is carried out. The extraction of zirconium from the liquid alloy can be achieved using general metallurgical separation methods (such as molten salt electrolytic oxidation to separate zirconium from the liquid alloy). The final zirconium product obtained contains less than 100 ppm hafnium, which meets the requirement for hafnium in the nuclear-grade zirconium products.

Embodiment 1

[0029] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.3 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 800? C. and held at this temperature for 1 hour, potassium fluozirconate (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is added to the anode chamber, meanwhile a voltage is applied for electrolysis, and the current density is controlled at 0.02 A.Math.cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrates into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0030] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.007% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 2

[0031] The matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the liquid alloy is directly used as an anode and connected to the electric current for electrolysis, the zirconium is used as the cathode, the refractory ceramic is used as the lining of the cell body, the cathode electrolyte is prepared from NaCl and K.sub.2ZrF.sub.6 at a mass ratio of 1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C., the current density is controlled at 0.02 A cm.sup.?2, after 1 hour of electrolysis, the liquid alloy is taken out.

[0032] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.009% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 3

[0033] The matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the copper rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.2 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C. and held at this temperature for 1 hour, a voltage is applied for electrolysis, and the current density is controlled at 0.015 A cm.sup.?2, in the electrolysis process, the copper anode is continuously oxidized to the copper ions, the copper ions migrate into the anode electrolyte, the copper ions in the anode electrolyte are reduced to the copper metal at the interface between the anode electrolyte and the liquid alloy, and the copper metal migrates into the liquid alloy, meanwhile, the hafnium metal in the liquid alloy is oxidized to the hafnium ions, and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0034] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.005% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 4

[0035] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the zirconium metal (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.2 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C. and held at this temperature for 1 hour, a voltage is applied for electrolysis and the current density is controlled at 0.02 A.Math.cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrate into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0036] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.007% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 5

[0037] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl, KCl and NaF at a mass ratio of 1:1:0.1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.3 at a mass ratio of 1:1:0.01 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C. and held at this temperature for 1 hour, potassium fluozirconate (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is added to the anode chamber, meanwhile a voltage is applied for electrolysis, and the current density is controlled at 0.02 A.Math.cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrates into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0038] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.007% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 6

[0039] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.2 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C. and held at this temperature for 1 hour, ZrO.sub.2 (wherein the hafnium content accounts for 1.8% of the total mass of zirconium and hafnium) is slowly added to the anode chamber, meanwhile a voltage is applied for electrolysis, and the current density is controlled at 0.02 A cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrates into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0040] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.009% of the total mass of zirconium and hafnium, which meets the requirement for the hafnium content in nuclear-grade zirconium.

Embodiment 7

[0041] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 1:1, and 10 g of zirconium metal powder (wherein the hafnium content accounts for 5.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.2 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 900? C. and held at this temperature for 1 hour, potassium fluozirconate (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is added to the anode chamber, meanwhile a voltage is applied for electrolysis, and the current density is controlled at 0.02 A.Math.cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrates into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0042] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.012% of the total mass of zirconium and hafnium.

Embodiment 8

[0043] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 9:1, and 90 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) as the solute metal is added into the matrix metal; the zirconium metal (wherein the hafnium content accounts for 6.2% of the total mass of zirconium and hafnium) is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.2 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber. Under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 950? C. and held at this temperature for 1 hour, and then a voltage is applied for electrolysis and the current density is controlled at 0.02 A.Math.cm.sup.?2, the zirconium ions in the anode electrolyte are continuously reduced to the zirconium metal and the zirconium metal continuously migrates into the liquid alloy, the hafnium metal in the liquid alloy is oxidized to the hafnium ions and the hafnium ions migrate into the cathode electrolyte, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0044] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of hafnium accounts for 0.013% of the total mass of zirconium and hafnium.

[0045] The change of parameters in Embodiment 9 and Embodiment 10 compared to Embodiment 1 are shown in Table 1, other parameters in Embodiment 9 and Embodiment 10 are the same as in Embodiment 1, the experimental results are also presented in Table 1.

TABLE-US-00001 TABLE 1 Composition Embodi- of the liquid Electrolysis The anode The cathode Current Raw Product ment alloy temperature electrolyte electrolyte Anode Cathode density material purity 1 500g Cu:Sn 800? C. 300 g 300 g graphite stainless 0.02 Potassium Hf/ wt. % = 1:1 NaCl:KCl NaCl:KCl: steel A .Math. cm.sup.?2 fluoro- (Zr + Hf) = Then add wt. % = 1:1 ZrCl.sub.2 zirconate 0.007% 10 g wt. % = zirconium 1:1:0.02 powder (Hf content is 2.2 wt.%) 9 500 g Bi 400? C. 300 g 300 g graphite Tungsten 0.002 Potassium Hf/ Then add 1 g LiCl:KCl LiCl:KCl: A .Math. cm.sup.?2 fluoro- (Zr + Hf) = zirconium wt. % = 1:1 K.sub.2ZrF.sub.6 zirconate 0.005% powder (Hf wt. % = content is 1:1:0.02 1.8 wt. %) 10 500 g Cu 1100? C. 300 g 300 g graphite stainless 0.5 ZrO.sub.2 Hf/ Then add CaCl.sub.2 NaCl:KCl: steel A .Math. cm.sup.?2 (Zr + Hf) = 90 g K.sub.2ZrF.sub.6 0.009% zirconium wt. % = powder (Hf 2:1:0.02 content is 2.2 wt. %)

Comparative Embodiment 1

[0046] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 9:1; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.4 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 800? C. and held at this temperature for 1 hour, potassium fluozirconate (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is added to the anode chamber, meanwhile a voltage is applied for electrolysis, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0047] An elemental analysis is carried out on the metal phase in the liquid alloy, wherein the content of zirconium is low, therefore the separation of zirconium and hafnium is not achieved.

Comparative Embodiment 2

[0048] The electrolysis reaction is carried out in the electrolytic cell as shown in FIG. 1, the matrix metal of 500 g is prepared from copper and tin at a mass ratio of 9:1, and 90 g of zirconium metal powder (wherein the hafnium content accounts for 2.2% of the total mass of zirconium and hafnium) is added into the matrix metal as the solute metal; the graphite rod is used as the anode, the stainless steel is used as the cathode, the refractory ceramic is used as the lining of the cell body, the anode electrolyte is prepared from NaCl and KCl at a mass ratio of 1:1 and 300 g of the anode electrolyte is added into the anode chamber, the cathode electrolyte is prepared from NaCl, KCl and ZrCl.sub.4 at a mass ratio of 1:1:0.02 and 300 g of the cathode electrolyte is added into the cathode chamber, under the protection of argon atmosphere, the electrolytic cell is heated at a rate of 10? C./min to 800? C. and held at this temperature for 1 hour, after 6 hours of electrolysis, a sample is taken from the liquid alloy feed port.

[0049] An elemental analysis is carried out on the metal phase in the liquid alloy, the ratio of zirconium and hafnium in the alloy is not changed.

[0050] The above are only specific embodiments of the present disclosure, however, the protection scope of the present disclosure is not limited thereto, any modifications or substitutions readily apparent to those skilled in the art within the technical scope disclosed by the present disclosure should be encompassed within the scope of protection of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.