CN108441892B - Method for refining high-purity titanium through metastable state high-temperature molten salt electrolysis based on complex ions - Google Patents
Method for refining high-purity titanium through metastable state high-temperature molten salt electrolysis based on complex ions Download PDFInfo
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Abstract
The invention discloses a method for refining high-purity titanium by metastable state high-temperature molten salt electrolysis based on complex ions. In the metastable state high-temperature molten salt, titanium ions in the titanium ion source exist in the form of complex ions, wherein the titanium ions comprise high-valence titanium ions and low-valence titanium ions. The existence of the complex ions can reduce the power consumption loss caused by the disproportionation reaction of the titanium ions. And carrying out electrolytic refining in the metastable molten salt to obtain high-purity titanium, wherein the purity of the high-purity titanium can meet the requirement of 4N 5-5N, and the electrolytic efficiency is higher than 90%.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for refining high-purity titanium through metastable state high-temperature molten salt electrolysis based on complex ions.
Background
The high-purity titanium has excellent performances of light weight, corrosion resistance, low resistivity and the like, is mainly applied to industries such as large-scale integrated circuit manufacturing, high-end novel titanium alloy and the like, is a strategic key material necessary for electricians, electronics and aerospace, and plays a vital role in national safety and national defense construction. High purity titanium, as a sputtering target for manufacturing large scale integrated circuits, is required to have a purity of 4N5 grade (99.995%) to 6N grade (99.9999%), wherein the oxygen content is below 200ppm and the metal impurity content is below 10 ppm. However, the current technology for preparing high-purity titanium is immature, so that the price of the high-purity titanium is too high to a certain extent, and the high-purity titanium is directly not applied on a large scale.
In various preparation technologies of high-purity titanium, the fused salt electrolysis process which is simple in process and easy to realize continuity has a very wide application prospect and is paid much attention. The molten salt electrolysis method is to extract high-purity titanium by utilizing an electrochemical principle, and generally takes coarse titanium, titanium alloy or titanium compound as an anode, dissolves raw material titanium into an electrolyte at a certain precipitation potential, and precipitates the high-purity titanium at a cathode. Impurities with a higher dissolution potential than titanium remain on the anode or precipitate in the electrolyte during electrolysis, and impurities with a lower dissolution potential than titanium are also dissolved in the electrolyte together with titanium. For example, patent documents CN102517611A and CN104947152A disclose technical proposals for refining high-purity titanium by molten salt electrolysis, and patent documents CN102230193A, CN103014775A, CN104928719A, CN105568320A, CN201605337U, CN204982083U, CN204874773U and CN205653517U disclose apparatuses for refining high-purity titanium by molten salt electrolysis. However, in the prior art, the technical scheme of refining high-purity titanium by molten salt electrolysis generally uses alkali metal chloride as electrolyte molten salt, and titanium ions added in the electrolyte molten salt or electrochemically dissolved at an anode are Ti2+Or Ti3+Form exists in the meltIn salt, original Ti in molten salt2+And is composed of Ti3+Reduced Ti2+Disproportionation in molten salt
This causes a large power loss and a low electrolysis efficiency; moreover, the quality of the high-purity titanium is affected by the change of the product morphology caused by the change of the electrolytic composition.
Disclosure of Invention
In order to solve at least one of the above-mentioned technical problems of the prior art, the present invention discloses a method for refining high-purity titanium by electrolysis based on a metastable state high-temperature molten salt of complex ions, in which titanium ions exist stably in the form of complex ions.
According to the method for refining high-purity titanium through electrolysis of the metastable state high-temperature molten salt based on the complex ions, substances containing fluorine ions are added into the metastable state high-temperature molten salt, and the added fluorine ions and titanium ions form the complex ions.
According to the method for refining high-purity titanium through metastable state high-temperature molten salt electrolysis based on complex ions, disclosed by some embodiments of the invention, the molar ratio of fluorine ions to titanium ions is set to be 1: 1-15: 1.
Some embodiments of the invention disclose methods for refining high purity titanium by metastable high temperature molten salt electrolysis based on complex ions, the fluoride ion containing substance comprising an alkali metal or alkaline earth metal fluoride.
The invention discloses a method for refining high-purity titanium by metastable state high-temperature molten salt electrolysis based on complex ions, which comprises high-valence titanium ions and low-valence titanium ions.
According to the method for refining high-purity titanium by metastable state high-temperature molten salt electrolysis based on complex ions, disclosed by some embodiments of the invention, when the titanium ions are high-valence titanium ions, the high-valence titanium ions exist stably in the form of the complex ions; when the titanium ions are low-valence titanium ions, the low-valence titanium ions are converted into high-valence titanium ions, and then the high-valence titanium ions exist stably in the form of complex ions.
The invention discloses a method for refining high-purity titanium by electrolyzing metastable state high-temperature molten salt based on complex ions, wherein titanium ions are provided by a titanium ion source, and the weight content of the titanium ion source in the metastable state high-temperature molten salt is set between 2.0 and 15.0 percent.
The invention discloses a method for refining high-purity titanium by electrolyzing metastable state high-temperature molten salt based on complex ions, which comprises LiCl and MgCl2、LiCl-KCl、LiCl-RbCl、LiCl-CsCl、MgCl2-LiCl、MgCl2-NaCl、MgCl2-KCl、MgCl2-RbCl、CaCl2-LiCl、CaCl2-NaCl、NaCl、KCl、RbCl、CsCl、CaCl2、NaCl-KCl、NaCl-RbCl、NaCl-CsCl、MgCl2-CsCl、CaCl2-KCl、CaCl2-RbCl。
In the method for refining high-purity titanium by electrolyzing the metastable state high-temperature molten salt based on the complex ions, disclosed by some embodiments of the invention, the metastable state high-temperature molten salt is subjected to pre-melting refining treatment before electrolysis.
The invention discloses a method for refining high-purity titanium by metastable state high-temperature molten salt electrolysis based on complex ions, which comprises the following steps:
(i) pre-melting the main electrolyte;
(ii) adding other electrolyte which forms eutectic salt with the main electrolyte;
(iii) fully mixing the main electrolyte with other electrolytes at a temperature 50 ℃ above the eutectic temperature to form eutectic salt electrolyte;
(iv) heating eutectic salt electrolyte under vacuum, wherein the heating temperature is set between 100 and 300 ℃, and the vacuum degree is set at 10-2～10-5Pa, the holding time is set to be 6-12 hours;
(v) respectively heating the eutectic salt electrolyte to the melting point and the temperature 50 ℃ above the eutectic point in the argon atmosphere, carrying out secondary remelting, and keeping for 24 hours;
(vi) and deoxidizing the eutectic salt electrolyte by using hydrogen chloride gas, wherein the treatment time is set to be 1-3 hours.
The method disclosed by the invention changes the existence state of titanium ions in the molten salt by changing the electrolyte components and adding the fluorine-containing ion substance as the additive, so that complex ions with stronger stability are formed, the influence of the disproportionation reaction of the titanium ions in the molten salt electrolysis process is reduced, the electrolysis efficiency is improved, and the high-purity titanium is obtained by electrolytic refining in the metastable molten salt, the purity of the high-purity titanium can meet the requirement of 4N 5-5N, and the electrolysis efficiency is higher than 90%.
Drawings
FIG. 1 is a schematic diagram of the principle of refining high-purity titanium by metastable state high-temperature molten salt electrolysis based on complex ions
FIG. 2 is a graph of samples obtained in examples 1 to 3 of the present disclosure
Detailed Description
The word "embodiment" as used herein, is not necessarily to be construed as preferred or advantageous over other embodiments, including any embodiment illustrated as "exemplary". The performance index measurements in the examples of this method, unless otherwise indicated, were carried out using test methods conventional in the art. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; other raw materials, reagents, test methods and technical means not specifically mentioned as the present invention refer to those generally used by those of ordinary skill in the art, and those generally used; molten salt electrolytes described in the present disclosure include, but are not limited to, elemental electrolytes, which generally refers to an elemental electrolyte, such as LiCl; the eutectic salt electrolyte refers to a mixed electrolyte formed by mixing two or more elementary electrolytes, wherein the mixed electrolyte has a eutectic point, and the ratio of the components in the eutectic salt with the eutectic point is constant, such as the eutectic salt electrolyte formed by LiCl and KCl, wherein the molar ratio of the LiCl to the KCl is 0.59: 0.41; the main electrolyte mentioned in the disclosure generally refers to the main component in the eutectic salt, and the other electrolytes refer to other components except the main electrolyte in the eutectic salt; the higher valence titanium ions are generally referred toTrivalent titanium ion Ti3+The lower valence titanium ion is usually referred to as a divalent titanium ion Ti2+(ii) a Substances containing fluoride ions, generally capable of releasing F in metastable high-temperature molten salts-Fluoride ion species including but not limited to sodium fluoride, potassium fluoride; the titanium ion source generally refers to a substance capable of releasing titanium ions in high temperature molten salt, including but not limited to titanium dichloride, titanium trichloride; molar content generally refers to moles/mole and weight content generally refers to weight/weight.
The terms "substantially" and "about" are used throughout this disclosure to describe small fluctuations. For example, they may mean less than or equal to ± 5%, such as less than or equal to ± 2%, such as less than or equal to ± 1%, such as less than or equal to ± 0.5%, such as less than or equal to ± 0.2%, such as less than or equal to ± 0.1%, such as less than or equal to ± 0.05%. Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. Such range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of "1% to 5%" should be interpreted to include not only the explicitly recited values of 1% to 5%, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values, such as 2%, 3.5%, and 4%, and sub-ranges, such as 1% to 3%, 2% to 4%, and 3% to 5%, etc. This principle applies equally to ranges reciting only one numerical value. Moreover, such an interpretation applies regardless of the breadth of the range or the characteristics being described.
In this disclosure, including the claims, all conjunctions such as "comprising," including, "" carrying, "" having, "" containing, "" involving, "" containing, "and the like are to be understood as being open-ended, i.e., to mean" including but not limited to. The conjunctive words "consisting of" and "consisting essentially of" should be closed or semi-closed conjunctive words only.
In the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In the examples, some methods, means, apparatuses, devices, raw material compositions, molecular structures, etc. known to those skilled in the art are not described in detail in order to highlight the gist of the present invention.
In some embodiments, a substance containing fluoride ions is added to the metastable high-temperature molten salt, and the titanium ions in the titanium ion source and the added fluoride ions form complex ions. In some embodiments, the source of titanium ions is a high valence titanium ion Ti3+The substance containing fluorinion is added into the molten salt electrolyte as an additive, and can effectively complex with high-valence titanium ion Ti in the molten salt3+To form complex ions:
TiCl6-iFi 3-wherein x is an integer of 1 to 6
The stable presence of the complexing ion allows Ti in the molten salt electrolyte3+The ion concentration is the largest ratio in the total concentration of the titanium ions, and the average valence of the titanium ions in the molten salt is more than 2.8. In turn, Ti can be used in the electrochemical reduction process3+To three electron one-step reduction of metallic titanium.
In some embodiments, the source of titanium ions is a low valence titanium ion Ti2+Low valence Ti ions in electrolyte molten salt2+Disproportionation reaction and high valence Ti ion3+Coexisting, an equilibrium state is formed as shown by the following formula:
the substance containing fluorinion is added into the molten salt electrolyte as an additive, and can effectively complex with high-valence titanium ion Ti in the molten salt3+Forming a complex ion, the stable presence of which allows the formation of a low valence Ti ion in the molten salt electrolyte2+The ion concentration is reduced, and the valence of Ti ion is high3+The ratio of Ti ions to Ti ions is the largest, and Ti ions can be used for electrochemical reduction3+To three electron one-step reduction of metallic titanium.
The fluoride ion-containing substance generally added includes alkali metal or alkaline earth metal fluorides, for example, sodium fluoride, potassium fluoride, and the like. Sodium fluoride, potassium fluoride, and the like release fluoride ions in the electrolyte molten salt. In some embodiments of the invention, the molar ratio of the fluorine ion-containing substance to the titanium ion source is 1:1 to 15: 1; a more preferable embodiment is 2:1 to 12:1, and a still more preferable embodiment is 3:1 to 10: 1.
Generally, the titanium ion source includes a low valence titanium-containing substance and a high valence titanium-containing substance; typically the lower valence titanium comprises Ti2+TiCl can be selected as the material of the low-valent titanium ion source2With TiCl3Mixing salt; typically the higher valence titanium comprises Ti3+TiCl can be selected as the high valence titanium ion source3. Usually TiCl is mixed2Is prepared into Ti ions containing low valence titanium ions by being mixed with electrolyte or eutectic salt electrolyte2+As an alternative to adding a source of titanium ions, a molten salt of (2).
In some embodiments, the metastable high-temperature molten salt used comprises LiCl, MgCl2、LiCl-KCl、LiCl-RbCl、LiCl-CsCl、LiCl-NaCl、KCl-CsCl、MgCl2-LiCl、MgCl2-NaCl、MgCl2-KCl、MgCl2-RbCl、CaCl2-LiCl、CaCl2-NaCl、NaCl、KCl、RbCl、CsCl、CaCl2、NaCl-KCl、NaCl-RbCl、NaCl-CsCl、MgCl2-CsCl、CaCl2-KCl、CaCl2-RbCl、CaCl2-CsCl. The compositions and proportions of the eutectic salt electrolytes described above are listed in table 1.
TABLE 1 eutectic salt electrolyte compositions and their molar ratios
In the metastable state high-temperature molten salt electrolytic refining of high-purity titanium based on complex ions, the metastable state molten salt is subjected to pre-melting refining treatment before electrolysis. Specifically, the premelting refining treatment comprises the following steps:
(i) pre-melting the main electrolyte;
(ii) adding other electrolyte which forms eutectic salt with the main electrolyte;
(iii) fully mixing the main electrolyte with other electrolytes at a temperature 50 ℃ above the eutectic temperature to form eutectic salt electrolyte;
(iv) heating eutectic salt electrolyte under vacuum, wherein the heating temperature is set between 100 and 300 ℃, and the vacuum degree is set at 10-2～10-5Pa, the holding time is set to be 6-12 hours; namely removing water existing in the eutectic salt electrolyte under the vacuum environment condition;
(v) respectively heating the eutectic salt electrolyte to the melting point and the temperature 50 ℃ above the eutectic point in the argon atmosphere, carrying out secondary remelting, and keeping for 24 hours; usually, after removing water in the eutectic salt electrolyte, filling high-purity argon into a vacuum environment, and carrying out secondary remelting at a temperature 50 ℃ above the melting point temperature of the monomer electrolyte and the eutectic point temperature of the eutectic salt electrolyte respectively under the protection of the argon;
(vi) deoxidizing the eutectic salt electrolyte by using hydrogen chloride gas, wherein the treatment time is set to be 1-3 hours; the twice remelted eutectic salt electrolyte is typically treated in the presence of hydrogen chloride gas to remove oxygen therefrom. In general, after the removal of oxygen is completed, it is necessary to replace the hydrogen chloride gas with an inert gas such as argon gas in order to remove the hydrogen chloride gas.
In general, (i), (ii), and (iii) in the prefusion purification treatment may be collectively referred to as prefusion treatment, and (iv), (v), and (vi) may be collectively referred to as purification treatment. As some embodiments, the pre-melting treatment and the refining treatment may be performed separately. In the pre-melting treatment and the refining treatment, if the simple substance molten salt is used as the electrolyte, the main electrolyte is the simple substance electrolyte, and meanwhile, the steps related to other electrolytes are omitted.
In some embodiments of the invention, in the method for electrolytic refining of high-purity titanium by using low-valence titanium as a titanium ion source, after pre-melting refining treatment is performed on eutectic salt electrolyte, a substance containing low-valence titanium ions is added into the eutectic salt electrolyte, and then a fluorine-containing ion substance is added into the eutectic salt electrolyte to uniformly mix ions in molten salt, wherein the low-valence titanium ions Ti are titanium ions2+Converted into high valence titanium ion Ti3+And further Ti3+The form of complex ion is stabilized in electrolyte molten salt to obtain Ti3+The concentration has an absolute ratio of the molten salt electrolyte.
In some embodiments of the invention, in a method for electrolytic refining of high purity titanium using high valence titanium as a titanium ion source, a fluorine ion-containing substance is added to a eutectic salt electrolyte to perform a pre-melting refining process, and a high valence titanium ion-containing substance, such as powdered titanium trichloride, is added to the eutectic salt electrolyte at a temperature 50 ℃ higher than the eutectic temperature of the eutectic salt electrolyte to uniformly mix ions in the molten salt, thereby obtaining high valence titanium ions, Ti3+Stably existing in the molten salt electrolyte in the form of complex ions to obtain Ti3+The concentration has an absolute ratio of the molten salt electrolyte.
The titanium complex ions stably existing in the electrolyte molten salt participate in the electrolytic reaction process of electrorefining high-purity titanium, as illustrated in fig. 1, the titanium complex ions are gradually deposited on a cathode in the constant current electrolytic process to obtain high-purity titanium metal, an anode is gradually consumed, and the titanium complex ions are dissolved in the electrolyte molten salt in the form of titanium ions to form titanium complex ions to supplement the titanium complex ions consumed in the electrolyte.
In the present disclosure, the electrolytic efficiency of the metastable high-temperature molten salt electrolytic refining of high-purity titanium is calculated according to formula (1). The calculation formula (1) of the electrolytic efficiency is:
in formula (1): m isaM for actually obtaining the electrolytic product masstFor the theoretical product quality according to faraday's law, the following equation (2) is used:
in formula (2): i is the actual electrolysis current, t is the actual electrolysis time, MTiIs the mass of the metal titanium atom, Z is the valence state of the discharge ion, and F is the Faraday constant.
In some embodiments of the invention, the electrorefining of high-purity titanium in metastable high-temperature molten salt is carried out according to the following method, which specifically comprises the following steps:
pre-melting and refining eutectic salt electrolyte;
placing the eutectic salt electrolyte subjected to pre-melting refining treatment in an alumina crucible, and adding a titanium ion source to obtain a premix; heating the mixture to a melting temperature, for example, 750 ℃, under the protection of argon gas, so that the ions are fully and uniformly mixed to obtain a prepared molten salt with homogeneous titanium ions; adding a fluoride ion source into the prepared molten salt in proportion, and keeping the preset time at the working temperature when the fluoride ion is fully complexed with the titanium ion, wherein the preset time is usually 12-24 hours; cooling;
two anodes and one cathode are used as electrolysis electrodes, the electrode distance is reasonably arranged, the electrodes are placed in a furnace body, the furnace body is ensured to be sealed, and the furnace body is vacuumized; cleaning the furnace chamber by using high-purity argon at a set temperature, and arranging positive pressure protection; for example, the oven cavity may be cleaned at 300 ℃; after the temperature is raised to the melting temperature, the temperature is preserved, and the electrode is slowly put into the molten salt; carrying out constant current electrolysis under constant current density; the constant current is usually set at 0.1-1.5A/cm2To (c) to (d); after the electrolysis is finished, placing the electrode above the molten salt, and draining the salt in the product; opening the furnace, taking out the cathode, and placing the cathode plate deposited with the high-purity titanium product in deionized water for ultrasonic washing; and (3) drying the washed cathode product in a vacuum oven to obtain the high-purity titanium metal, wherein the drying temperature can be set to be 50 ℃, for example.
Example 1
Pre-melting and refining NaCl-KCl (0.5:0.5) eutectic salt electrolyte according to the method disclosed by the invention;
placing the pre-melted and refined NaCl-KCl eutectic salt in an alumina crucible, and adding NaCl-KCl-TiCl containing low-valence titanium ions2Melting the salt into the crucible to make TiCl2The content in the molten salt is 4.5 percent; heating the mixture to 750 ℃ under the protection of argon gas, and fully and uniformly mixing all ions to obtain a prepared molten salt with homogeneous titanium ions; KF is taken as a fluoride ion source and is proportionally added into the prepared molten salt, and the molar ratio of the fluoride ion to the low-valence titanium ion in the embodiment 1 is 2.0. Keeping the working temperature for 24 hours after the fluorine ions are fully complexed with the titanium ions, and cooling;
two anodes and one cathode are used as electrolysis electrodes, the electrode distance is reasonably arranged, the electrodes are placed in a furnace body, the furnace body is ensured to be sealed, and the furnace body is vacuumized; cleaning the furnace chamber with high-purity argon at 300 ℃, and placing positive pressure protection; after the temperature is raised to 750 ℃, preserving the heat for 2 hours, and slowly putting the electrode into the molten salt; at a current density of 0.5A/cm2Carrying out constant current electrolysis under the condition of (1); after the electrolysis is finished, placing the electrode at a position 3-5 cm above the molten salt, and draining the salt in the product; opening the furnace, taking out the cathode, and placing the cathode plate deposited with the high-purity titanium product in deionized water for ultrasonic washing; and (4) putting the washed cathode product into a vacuum oven at 50 ℃ and drying to obtain the high-purity titanium metal.
FIG. 2(a) is a diagram showing a sample of high purity titanium obtained in example 1. It can be seen that the high purity titanium is granular crystalline with a distinct metallic luster.
The electrolytic efficiency of this example 1 calculated according to the formulas (1) and (2) is about 91.7%, wherein the discharge ion valence is 3.
Example 2
Pre-melting and refining NaCl-KCl (0.5:0.5) eutectic salt electrolyte according to the method disclosed by the invention;
placing the pre-melted and refined NaCl-KCl eutectic salt in an alumina crucible, and adding NaCl-KCl-TiCl containing low-valence titanium ions2Melting the salt into the crucible to make TiCl2The content of (b) in the molten salt is 2.5%; heating the mixture to 750 ℃ under the protection of argon to fully and uniformly mix all ions to obtain the preparation with homogeneous titanium ionsMelting a salt; KF is taken as a fluoride ion source and is proportionally added into the prepared molten salt, and the molar ratio of the fluoride ion to the low-valence titanium ion in the embodiment 2 is 4.0. Keeping the working temperature for 24 hours after the fluorine ions are fully complexed with the titanium ions, and cooling;
two anodes and one cathode are used as electrolysis electrodes, the electrode distance is reasonably arranged, the electrodes are placed in a furnace body, the furnace body is ensured to be sealed, and the furnace body is vacuumized; cleaning the furnace chamber with high-purity argon at 300 ℃, and placing positive pressure protection; after the temperature is raised to 750 ℃, preserving the heat for 2 hours, and slowly putting the electrode into the molten salt; at a current density of 0.5A/cm2Carrying out constant current electrolysis under the condition of (1); after the electrolysis is finished, placing the electrode 5cm above the molten salt, and draining the salt in the product; opening the furnace, taking out the cathode, and placing the cathode plate deposited with the high-purity titanium product in deionized water for ultrasonic washing; and (4) putting the washed cathode product into a vacuum oven at 50 ℃ and drying to obtain the high-purity titanium metal.
FIG. 2(b) is a diagram showing a sample of high purity titanium obtained in example 2. It can be seen that the high purity titanium is predominantly granular crystalline with a small amount of powdered titanium.
The electrolytic efficiency of this example 2 calculated according to the formulas (1) and (2) is about 93.1%, wherein the valence of the discharge ion is 3.
Example 3
Pre-melting and refining NaCl-KCl (0.5:0.5) eutectic salt electrolyte according to the method disclosed by the invention;
placing the pre-melted and refined NaCl-KCl eutectic salt in an alumina crucible, adding TiCl3Into the crucible, TiCl is caused to3The content in the molten salt is 4.0 percent; heating the mixture to 750 ℃ under the protection of argon gas, fully and uniformly mixing all ions, and standing for about 6 hours to obtain prepared molten salt with homogeneous titanium ions; NaF is used as a fluoride ion source and is proportionally added into the prepared molten salt, and the molar ratio of the fluoride ion to the high-valence titanium ion in the embodiment 3 is 6.0. Keeping the working temperature for 24 hours after the fluorine ions are fully complexed with the titanium ions, and cooling;
two anodes and one cathode are used as electrolysis electrodes, the electrode distance is reasonably arranged, the electrodes are placed in a furnace body, and the furnace is ensuredSealing the body and vacuumizing; cleaning the furnace chamber with high-purity argon at 300 ℃, and placing positive pressure protection; after the temperature is raised to 750 ℃, preserving the heat for 2 hours, and slowly putting the electrode into the molten salt; at a current density of 0.5A/cm2Carrying out constant current electrolysis under the condition of (1); after the electrolysis is finished, placing the electrode 5cm above the molten salt, and draining the salt in the product; opening the furnace, taking out the cathode, and placing the cathode plate deposited with the high-purity titanium product in deionized water for ultrasonic washing; and (4) putting the washed cathode product into a vacuum oven at 50 ℃ and drying to obtain the high-purity titanium metal.
FIG. 2(c) is a graph showing a sample of high purity titanium obtained in example 3. It can be seen that the high purity titanium is granular crystal, and the grain size is relatively fine and uniform, and has metallic luster.
The electrolytic efficiency of this example 3 calculated according to the formulas (1) and (2) is about 94.6%, wherein the discharge ion valence is 3.
According to the method disclosed by the invention, the existence state of titanium ions in the molten salt is changed by adding the fluorine-containing additive, complex ions with stronger stability are formed, the influence of disproportionation reaction of the titanium ions in the molten salt electrolysis process is reduced, the electrolysis efficiency is improved, the purity of high-purity titanium obtained by electrolytic refining in the metastable molten salt can meet the requirement of 4N 5-5N, and the electrolysis efficiency is higher than 90%.
The technical solutions and the technical details disclosed in the embodiments of the present invention are only examples to illustrate the concept of the present invention, and do not limit the present invention, and all the non-inventive changes to the technical details disclosed in the present invention have the same inventive spirit as the present invention, and are within the scope of the claims of the present invention.
Claims (8)
1. The method for refining high-purity titanium by electrolyzing the metastable state high-temperature molten salt based on complex ions is characterized by comprising the steps of pre-melting refining treatment of the metastable state high-temperature molten salt, complexing of a titanium ion source and electrolytic refining of the titanium ion source, wherein the metastable state high-temperature molten salt is eutectic salt electrolyte or single electrolyte;
wherein the metastable state high-temperature molten salt is eutectic salt electrolyte, and the pre-melting refining treatment comprises the following steps:
(i) pre-melting a host electrolyte, wherein the host electrolyte is a main component in a eutectic salt electrolyte;
(ii) adding other electrolyte which forms eutectic salt with the main electrolyte;
(iii) fully mixing the main electrolyte with other electrolytes at a temperature 50 ℃ above the eutectic temperature to form eutectic salt electrolyte;
(iv) heating eutectic salt electrolyte under vacuum, wherein the heating temperature is set between 100 and 300 ℃, and the vacuum degree is set at 10-2~10-5Pa, the holding time is set to be 6-12 hours;
(v) heating the eutectic salt electrolyte to a temperature 50 ℃ above the eutectic point in an argon atmosphere, carrying out secondary remelting, and keeping for 24 hours;
(vi) deoxidizing the eutectic salt electrolyte by using hydrogen chloride gas, wherein the deoxidizing treatment time is set to be 1-3 hours;
if the metastable state high-temperature molten salt is a single electrolyte, the premelting refining treatment comprises the following steps:
(i) pre-melting a single electrolyte;
(ii) melting the single electrolyte at a temperature 50 ℃ above the melting point to form a molten electrolyte;
(iii) heating the molten electrolyte under vacuum, wherein the heating temperature is set to be 100-300 ℃, and the vacuum degree is set to be 10-2~10-5Pa, the holding time is set to be 6-12 hours;
(iv) heating the molten electrolyte to a temperature 50 ℃ above the melting point in an argon atmosphere, carrying out secondary remelting, and keeping for 24 hours;
(v) deoxidizing the molten electrolyte by using hydrogen chloride gas, wherein the deoxidizing treatment time is set to be 1-3 hours;
the source of titanium ions complexing comprises:
placing eutectic salt electrolyte or single electrolyte after pre-melting refining treatment in an alumina crucible, adding a titanium ion source to obtain a premixed solutionA compound; the titanium ion source is a substance containing low-valence titanium or a substance containing high-valence titanium, and the substance containing low-valence titanium is TiCl2With TiCl3Mixed salts, or TiCl2Molten salt prepared with eutectic salt electrolyte or single electrolyte, the substance containing high valence titanium is TiCl3；
Heating the mixture to a melting temperature under the protection of argon gas, and fully and uniformly mixing all ions to obtain a prepared molten salt with homogeneous titanium ions;
adding a fluoride ion source into the prepared molten salt in proportion, and cooling after the fluoride ions and the titanium ions are fully complexed and the working temperature is kept for 12-24 hours;
in the electrolytic refining process of the titanium ion source, titanium ions exist stably in the form of complex ions in the metastable high-temperature molten salt.
2. The metastable state high-temperature molten salt electrolytic refining method of high-purity titanium based on complex ion according to claim 1, characterized in that a substance containing fluorine ion is added to the metastable state high-temperature molten salt, and the fluorine ion forms complex ion with the titanium ion.
3. The metastable state high-temperature molten salt electrolysis refining method for high-purity titanium based on complex ion according to claim 2, wherein the molar ratio of the fluorine ion to the titanium ion is set to 1: 1-15: 1.
4. The metastable high-temperature molten salt electrolytic refining method of high-purity titanium based on complex ion according to claim 3, characterized in that the fluoride ion-containing substance comprises an alkali metal or alkaline earth metal fluoride.
5. The metastable state high-temperature molten salt electrolytic refining method of high-purity titanium based on complex ion according to claim 1, characterized in that the titanium ion comprises a higher valence titanium ion and a lower valence titanium ion.
6. The metastable state high-temperature molten salt electrolysis refining method for high-purity titanium based on complex ion according to claim 5, characterized in that when the titanium ion is a high valence titanium ion, the high valence titanium ion exists stably in the form of complex ion; when the titanium ions are low-valence titanium ions, the low-valence titanium ions are converted into high-valence titanium ions, and then the high-valence titanium ions exist stably in a complex ion form.
7. The metastable high-temperature molten salt electrolysis refining method for high-purity titanium based on complex ion according to claim 1, characterized in that the titanium ion is provided by a titanium ion source, and the weight content of the titanium ion source in the metastable high-temperature molten salt is set between 2.0% and 15.0%.
8. The method for refining high-purity titanium by the metastable state high-temperature molten salt electrolysis based on complex ions according to claim 1, wherein the metastable state high-temperature molten salt comprises: LiCl, MgCl2、LiCl-KCl、LiCl-RbCl、LiCl-CsCl、MgCl2-LiCl、MgCl2-NaCl、MgCl2-KCl、MgCl2-RbCl、CaCl2-LiCl、CaCl2-NaCl、NaCl、KCl、RbCl、CsCl、CaCl2、NaCl-KCl、NaCl-RbCl、NaCl-CsCl、MgCl2-CsCl、CaCl2-KCl、CaCl2-RbCl。
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