Method for recovering metallic titanium from waste titanium material

Abstract

The invention provides a method for recovering metallic titanium from a waste titanium material, which comprises the following steps of: crushing the waste titanium material, and removing impurities to obtain an impurity-removed titanium material; the metal titanium precursor is obtained through segmented diaphragm electrolysis with fluoride fused salt as electrolyte and the titanium material after impurity removal as an anode, and the segmented diaphragm electrolysis comprises electrolysis for 2-6 h at the current density of 1.2 A / cm < 2 >-2.0 A / cm < 2 > and then electrolysis for 4-12 h at the current density of 0.2 A / cm < 2 >-0.6 A / cm < 2 >; and the metal titanium precursor is cleaned and then subjected to vacuum distillation, and metal titanium is obtained. By means of the method, complex waste titanium materials can be treated, no waste liquid is generated, and the recycled product titanium is of a dendritic crystal structure, high in purity and excellent in physical and chemical performance.

Description

Technical Field

[0001] The present invention relates to the field of titanium recovery, and more particularly, to a method for recovering metallic titanium from waste titanium materials. Background Art

[0002] Titanium and its alloys are widely used in fields such as aerospace, chemical industry, and medical due to their excellent strength, corrosion resistance, and biocompatibility. However, the production cost of titanium metal is high, mainly due to its complex smelting process, high energy consumption, and dependence on high-grade raw materials. With the continuous growth of the demand for titanium resources, recovering metallic titanium from waste titanium materials has become an important way to reduce production costs and achieve resource recycling.

[0003] Currently, the main methods for recovering metallic titanium from waste titanium materials include smelting method, chemical method, electrolysis method, and hydrogenation-dehydrogenation method. The smelting method is to mix waste titanium materials with fresh titanium materials and remelt them through methods such as vacuum arc melting or electron beam melting to obtain recycled titanium ingots. This method has a mature process and can directly obtain high-purity titanium metal, but it has high requirements for the purity of waste titanium materials, high energy consumption, large equipment investment, and it is difficult to process waste titanium materials containing oxides or nitrides. The chemical method converts titanium in waste titanium materials into soluble compounds through chemical methods such as acid leaching, alkali fusion, or chlorination, and then obtains metallic titanium through purification and reduction. This method is suitable for treating low-grade waste titanium materials, but the process flow is complex, generates a large amount of waste liquid, has a high risk of environmental pollution, and the cost of chemical reagents is high, with poor economy and it is difficult to achieve continuous production. The electrolysis method uses waste titanium materials as the anode and electrolyzes them in a molten salt electrolyte, and titanium ions are reduced and deposited as metallic titanium at the cathode. This method can directly obtain titanium and is suitable for treating complex waste titanium materials, but the electrolysis energy consumption is high and the purity of the product titanium is low. The hydrogenation-dehydrogenation method reacts waste titanium materials with hydrogen at high temperature to generate titanium hydride, and then obtains metallic titanium powder through dehydrogenation treatment. This method is suitable for preparing titanium powder, and the process is relatively simple, but it has high requirements for the composition of waste titanium materials, and the hydrogenation-dehydrogenation process has high energy consumption. Based on this, aiming at the defects existing in the prior art, there is an urgent need for a new method for treating waste titanium materials to provide a feasible technical solution for the efficient recycling of titanium resources. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, one of the purposes of the present invention is to solve one or more of the problems existing in the above prior art. For example, one of the purposes of the present invention is to provide a method for recovering metallic titanium from waste titanium materials that can treat complex waste titanium materials, produce no waste liquid, and has a short process flow.

[0005] The present invention provides a method for recovering metallic titanium from waste titanium materials, which may include the following steps: crushing the waste titanium materials and then performing impurity removal treatment to obtain the titanium materials after impurity removal; using a fluoride molten salt as an electrolyte and the titanium materials after impurity removal as an anode to perform segmented diaphragm electrolysis to obtain a metallic titanium precursor. Among them, the segmented diaphragm electrolysis may include electrolyzing at a current density of 1.2 A / cm 2 ~2.0 A / cm 2 for 2 h to 6 h and then electrolyzing at a current density of 0.2 A / cm 2 ~0.6 A / cm 2 for 4 h to 12 h; cleaning the metallic titanium precursor and then performing vacuum distillation to obtain metallic titanium.

[0006] Further, it may also include adding an active medium TiF3 to the electrolyte.

[0007] Further, the addition amount of the active medium TiF3 may be 5% to 8% of the mass of the electrolyte.

[0008] Further, the diaphragm may be a yttria-stabilized zirconia ceramic diaphragm, the thickness of the diaphragm may be 1.2 mm to 1.8 mm, the porosity of the diaphragm may be 25% to 30%, and the pore diameter may be <5 μm.

[0009] Further, the impurity removal treatment may include performing classification magnetic separation on the crushed waste titanium materials. Among them, the magnetic field intensity used in the first-stage magnetic separation may be 1.2 T to 1.5 T, and the magnetic field intensity used in the second-stage magnetic separation may be 0.8 T to 1.0 T.

[0010] Further, the fluoride molten salt may be a mixture of KF and NaF, and the molar ratio of KF to NaF may be 1:(1 to 3).

[0011] Further, the electrolysis temperature may be 700 °C to 800 °C.

[0012] Further, the segmented diaphragm electrolysis may include electrolyzing at a current density of 1.5 A / cm 2 ~1.8 A / cm 2 for 3 h to 5 h and then electrolyzing at a current density of 0.3 A / cm 2 ~0.5 A / cm 2 for 6 h to 10 h.

[0013] Compared with the prior art, the beneficial effects of the present invention at least include: the method of the present invention can process complex waste titanium materials, without generating waste liquid, and the recovered product titanium has a dendritic structure, high purity, and excellent physical and chemical properties. Description of the Drawings

[0014] The above and other objects and features of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, wherein:

[0015] Figure 1 This is the SEM image of the product obtained in Example 1 of the present invention.

[0016] Figure 2 This is the SEM image of the product obtained in Comparative Example 1. Detailed Description of the Invention

[0017] Hereinafter, a method for recovering metallic titanium from waste titanium materials according to the present invention will be described in detail in conjunction with the accompanying drawings and exemplary embodiments.

[0018] One aspect of the present invention provides a method for recovering metallic titanium from waste titanium materials. In some embodiments, the method may include the following steps:

[0019] S01, crushing the waste titanium materials and then performing impurity removal treatment to obtain the titanium materials after impurity removal.

[0020] S02, using a fluoride molten salt as an electrolyte and the titanium materials after impurity removal as an anode to perform segmented diaphragm electrolysis to obtain a metallic titanium precursor. Among them, the segmented diaphragm electrolysis includes electrolyzing at a current density of 1.2 A / cm 2 ~2.0 A / cm 2 for 2 h to 6 h and then electrolyzing at a current density of 0.2 A / cm 2 ~0.6 A / cm 2 for 4 h to 12 h.

[0021] S03, cleaning the metallic titanium precursor and then performing vacuum distillation to obtain metallic titanium.

[0022] In some embodiments, the waste titanium materials may be waste titanium materials such as TA1 and TA2.

[0023] In some embodiments, the crushing of the waste titanium materials can be carried out in a jaw crusher. The particle size of the crushed waste titanium materials can be 80 mesh to 120 mesh. At this particle size, it is convenient for subsequent impurity removal processes and makes the impurity removal more thorough. For example, the particle size of the crushed waste titanium materials can be 90 mesh or 100 mesh.

[0024] In some embodiments, impurity removal can be carried out by staged magnetic separation to remove impurity metals such as Fe, Ni, Cr, etc. from waste titanium materials. Preferably, it can be set to two-stage magnetic separation. The first-stage magnetic separation is strong magnetic separation. Under a magnetic field strength of 1.2 T to 1.5 T, using non-magnetic stainless steel wool medium (filling rate 50% - 55%), strong magnetic components such as Fe / Ni / Cr alloys are removed. The second-stage magnetic separation is carried out under a magnetic field strength of 0.8 T to 1.0 T, using flake medium (filling rate 30% - 35%) to separate weakly magnetic impurities included in inclusions. Setting the first-stage magnetic separation and the second-stage magnetic separation to a "strong first and then weak" magnetic field strength configuration can enable different magnetic impurities in the titanium material to be stripped in stages, making the impurity removal more thorough. For example, the magnetic field strength used in the first-stage magnetic separation can be set to 1.3 T to 1.4 T, and the magnetic field strength used in the second-stage magnetic separation can be set to 0.85 T to 0.95 T.

[0025] In some embodiments, the electrolyte can be a fluoride molten salt electrolyte. Compared with chloride molten salts, using fluoride molten salts as the electrolyte requires a lower electrolysis temperature. In certain embodiments, the electrolyte can be KF and / or NaF. For example, when the electrolyte is a mixture composed of KF and NaF, the molar ratio of KF to NaF can be set to 1:(1 - 3). Preferably, the molar ratio of KF to NaF can be 3:7.

[0026] In some embodiments, it also includes adding an active medium TiF3 to the electrolyte. Adding the active medium TiF3 to the electrolyte, on the one hand, can improve the electrolysis efficiency of the preparation process and promote the electrolysis process of titanium; on the other hand, the addition of the active medium TiF3 can reduce the reduction potential of titanium ions, accelerate the dissolution and deposition process of titanium in the electrolysis reaction, and reduce energy consumption; on the other hand, the addition of TiF3 can regulate the nucleation and growth of titanium crystals and promote the formation of a uniform dendritic structure. As Figure 1 shown, if TiF3 is not added, the electrolytic product titanium is prone to appear coarse grains or pore defects. In certain embodiments, the addition amount of the active medium can be 5% - 8% of the mass of the electrolyte. If the addition amount of TiF3 is less than 5 wt%, the promoting effect of TiF3 on the migration of titanium ions is insufficient, and the electrolysis rate cannot be increased; if the addition amount of TiF3 is higher than 8 wt%, it will cause an increase in the viscosity of the electrolyte, hinder ion diffusion, and increase the volatilization loss of fluorides. Therefore, the addition amount of the active medium TiF3 is controlled at 5% - 8% of the mass of the electrolyte. For example, the addition amount of the active medium TiF3 can be 6% - 7% of the mass of the electrolyte. For another example, the addition amount of the active medium TiF3 can be 6.5% of the mass of the electrolyte.

[0027] In some embodiments, the electrolysis temperature can be 700 °C to 800 °C. For example, the electrolysis temperature can be 720 °C to 780 °C, 750 °C to 770 °C, or a combination of the above ranges.

[0028] In some embodiments, the electrolysis method can be diaphragm electrolysis, which can be carried out in a two-zone isolated electrolytic cell. The anode zone is filled with titanium material after impurity removal, and the cathode uses a molybdenum electrode. The diaphragm can be a yttria-stabilized zirconia (YSZ) ceramic diaphragm to achieve physical isolation between the anode and cathode zones. The diaphragm thickness can be 1.2 mm to 1.8 mm, the diaphragm porosity can be 25% to 30%, and the pore diameter can be <5 μm. With the above settings of diaphragm thickness, diaphragm porosity, and pore diameter, Ti 3+ plasma can migrate freely while blocking the passage of solid particles. For example, the diaphragm thickness can be 1.4 mm to 1.6 mm, the diaphragm porosity can be 26% to 28%, and the pore diameter can be 1 μm to 4 μm.

[0029] In some embodiments, the diaphragm electrolysis can be segmented electrolysis. The first-stage electrolysis can be high-current-density electrolysis, and the second-stage electrolysis can be low-current-density electrolysis. For example, the current density of the first-stage electrolysis can be 1.2 A / cm 2 ~2.0 A / cm 2 、1.3 A / cm 2 ~1.9 A / cm 2 、1.4 A / cm 2 ~1.8 A / cm 2 、1.5 A / cm 2 ~1.7 A / cm 2 or a combination of the above ranges. The current density of the second-stage electrolysis can be 0.2 A / cm 2 ~0.6 A / cm 2 、0.25 A / cm 2 ~0.55 A / cm 2 、0.3 A / cm 2 ~0.5 A / cm 2 or a combination of the above ranges. The time of the first-stage electrolysis can be 2 h to 6 h, 3 h to 5 h, 3.5 h to 4.5 h, or a combination of the above ranges. The time of the second-stage electrolysis can be 5 h to 11 h, 6 h to 10 h, 7 h to 9 h, or a combination of the above ranges. For example, the segmented diaphragm electrolysis can include electrolysis at a current density of 1.6 A / cm 2 for 4 h and then at 0.4 A / cm 2Electrolyze at a current density for 8 h. During the first-stage electrolysis process set above, due to the use of a high current density, large-sized nuclei of titanium can be rapidly generated within a short time, preferentially removing high-potential impurities such as Fe and Al, reducing the interference of impurities on the dendritic structure, and avoiding the decrease in deposition efficiency caused by impurity interference in a single-stage electrolysis, such as the brittle fracture of dendrites induced by oxygen impurities. In the second-stage electrolysis set above, a lower current density is used to reduce the deposition rate, match the diffusion rate of titanium ions with the growth rate of nuclei, induce the growth of dendrites along a specific orientation, improve the uniformity and mechanical properties of dendrites, promote the uniform diffusion of titanium ions and the longitudinal extension of dendrites, and enhance the tensile strength. By setting different two-stage current densities for electrolysis and adding an active medium TiF3 accounting for 5% - 8% of the electrolyte mass, the formation characteristics of dendritic titanium can be optimized through staged regulation, significantly improving the preparation efficiency and performance of dendritic titanium, making the product titanium have a good dendritic structure. The dendritic structure is a microscopic morphology formed by metallic titanium under specific electrolysis conditions, which can enhance mechanical strength, improve fracture toughness, and enhance corrosion resistance, and is especially suitable for titanium materials required in high-end fields such as medical and aerospace. In addition, the ion mass transfer path is optimized, side reactions are reduced, the current efficiency is increased, the total energy consumption is reduced, it is applicable to the manufacture of high-performance structural parts, has an efficient impurity removal ability, reduces the comprehensive cost, and at the same time reduces pollution emissions.

[0030] In some embodiments, the metal titanium precursor can be cleaned by a combination of ultrasonic waves and organic solvents. The time for vacuum distillation treatment can be 3 h - 5 h, which can effectively remove low-boiling-point impurities such as Al and Mg.

[0031] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0032] Example 1

[0033] A method for recovering metallic titanium from waste titanium materials may include the following steps:

[0034] Step 01, crushing TA1 and TA2 waste titanium materials to a particle size of 90 mesh by a jaw crusher. Then magnetic separation is carried out, and the magnetic separation method is as follows:

[0035] First-stage strong magnetic separation: Using a magnetic field intensity of 1.3 T, through a stainless-steel permeable steel wool medium (filling rate 50%), removing impurities such as Fe, Ni, and Cr;

[0036] Second-stage gradient magnetic separation: Using a magnetic field intensity of 0.8 T, through a flaky neodymium iron boron magnetic medium (filling rate 30%), removing weakly magnetic impurities such as Al2O3.

[0037] Step 02, Purify by molten-salt electrolysis. Use KF-NaF (molar ratio 3:7) and add 6 wt% of TiF3 active medium as the electrolyte. Adopt diaphragm electrolysis, set the electrolysis temperature at 750 °C, fill the anode area with titanium material after magnetic separation, use a molybdenum rod as the cathode, control the current density at 1.2 A / cm 2 , electrolyze for 2 h, then adjust the current density to 0.4 A / cm 2 and conduct the second-stage electrolysis for 6 h. After the electrolysis is completed, collect the cathode product to obtain the metal titanium precursor.

[0038] Step 03, Use a 25 kHz ultrasonic frequency for the electrolysis product, the metal titanium precursor, and combine the volatility of ethanol with the ultrasonic cavitation effect to wash for 60 min, which can effectively strip the residual fluorinated salts and organic substances on the titanium surface. Then, perform vacuum distillation at a temperature of 700 °C for 5 h, with a vacuum degree ≤ 5×10 -3 Pa to deeply remove low-boiling-point impurities such as Al and Mg in titanium to achieve further purification and obtain high-purity metal titanium.

[0039] The purity of the product, metallic titanium, is determined by ICP-MS method and is greater than 99.93%. The SEM images are as Figure 1 shown, and its morphology presents a dendritic structure.

[0040] Example 2

[0041] A method for recovering metallic titanium from waste titanium materials may include the following steps:

[0042] Step 01, Crush TA1 and TA2 waste titanium materials to a particle size of 100 mesh using a jaw crusher. Then perform magnetic separation, and the magnetic separation methods include:

[0043] First-stage high-intensity magnetic separation: Adopt a magnetic field intensity of 1.4 T, and use a stainless-steel ferromagnetic steel wool medium (filling rate 52%) to remove impurities such as Fe, Ni, and Cr;

[0044] Second-stage gradient magnetic separation: Adopt a magnetic field intensity of 0.9 T, and use a flaky neodymium iron boron magnetic medium (filling rate 32%) to remove weakly magnetic impurities such as Al2O3.

[0045] Step 02, Purify by molten-salt electrolysis. Use KF-NaF (molar ratio 4:6) and add 7 wt% of TiF3 active medium, adopt diaphragm electrolysis, set the electrolysis temperature at 800 °C, fill the anode area with titanium material after magnetic separation, use a molybdenum rod as the cathode, control the current density at 1.4 A / cm 2 , electrolyze for 2 h, then adjust the current density to 0.6 A / cm 2 and conduct the second-stage electrolysis for 2 h. After the electrolysis is completed, collect the cathode product to obtain the metal titanium precursor.

[0046] Step 03: The metal titanium precursor of the electrolysis product is cleaned for 90 min using an ultrasonic frequency of 25 kHz, combining the volatility of ethanol and the ultrasonic cavitation effect, which can effectively strip the residual fluorides and organic substances on the titanium surface. Then, vacuum distillation is carried out at a temperature of 750 °C for 6 h, with a vacuum degree of ≤5×10 -3 Pa, to deeply remove low-boiling-point impurities such as Al and Mg in titanium to achieve further purification and obtain high-purity metal titanium.

[0047] The purity of the product metal titanium is determined by ICP-MS method, and its purity is greater than 99.95%.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference in this comparative example is that in Step 02, 6 wt% of TiF3 active medium was not added to the electrolyte, and the diaphragm electrolysis process was carried out at a constant current density of 0.8 A / cm 2 for 8 h. Others are the same as in Example 1.

[0050] The morphology of the product titanium obtained in this comparative example is as Figure 2 shown. Compared with the product titanium obtained in Example 1, without adding TiF3 active medium and without using two-stage electrolysis, the product titanium does not have a dendritic structure.

[0051] Although the present invention has been described above by combining exemplary embodiments, those skilled in the art should understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for recovering metallic titanium from waste titanium materials, characterized in that, It includes the following steps: Crush the waste titanium material and then conduct impurity removal treatment to obtain the titanium material after impurity removal; Using fluoride molten salt as the electrolyte and the titanium material after impurity removal as the anode, segmented diaphragm electrolysis is carried out to obtain a metal titanium precursor. Among them, the segmented diaphragm electrolysis includes electrolyzing at a current density of 1.2 A / cm 2 ~2.0 A / cm 2 for 2 h to 6 h and then electrolyzing at a current density of 0.2 A / cm 2 ~0.6 A / cm 2 for 4 h to 12 h; Clean the metal titanium precursor and then conduct vacuum distillation to obtain metallic titanium.

2. The method for recovering metallic titanium from waste titanium materials according to claim 1, wherein It also includes adding the active medium TiF3 to the electrolyte.

3. The method for recovering metallic titanium from waste titanium materials according to claim 2, characterized in that, The addition amount of the active medium TiF3 is 5% - 8% of the mass of the electrolyte.

4. The method for recovering metallic titanium from waste titanium materials according to any one of claims 1 to 3, characterized in that, The diaphragm is a yttria-stabilized zirconia ceramic diaphragm, the diaphragm thickness is 1.2 mm - 1.8 mm, the diaphragm porosity is 25% - 30%, and the pore diameter <5 μm.

5. The method for recovering metallic titanium from waste titanium materials according to any one of claims 1 to 3, characterized in that, The impurity removal treatment includes classifying and magnetic separating the crushed waste titanium material. Among them, the magnetic field intensity used for the first-stage magnetic separation is 1.2 T - 1.5 T, and the magnetic field intensity used for the second-stage magnetic separation is 0.8 T - 1.0 T.

6. The method for recovering metallic titanium from waste titanium materials according to any one of claims 1 to 3, characterized in that, The fluoride molten salt is a mixture of KF and NaF, and the molar ratio of KF to NaF is 1:(1 - 3).

7. The method for recovering metallic titanium from waste titanium materials according to any one of claims 1 to 3, characterized in that, The electrolysis temperature is 700 °C - 800 °C.

8. The method for recovering metallic titanium from waste titanium materials according to any one of claims 1 to 3, characterized in that, The segmented diaphragm electrolysis includes electrolyzing at a current density of 1.5 A / cm 2 ~1.8 A / cm 2 for 3 h to 5 h and then electrolyzing at a current density of 0.3 A / cm 2 ~0.5 A / cm 2 for 6 h to 10 h.

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