A method for the production of iron-containing pellets by reduction in a molten salt electrolytic cell

Abstract

The application relates to a method for preparing iron-containing small balls by reduction in a fused salt electrolytic cell and belongs to the technical field of non-ferrous metal metallurgy. Alkali metal chloride fused salt is uniformly ground and mixed, and then is placed in an alumina crucible, and water is removed in a vacuum drying box; the alumina crucible is placed in an electric resistance furnace inner container which is communicated with inert gas, after being heated and kept warm, micron Fe2O3 powder is added and completely mixed with the fused salt to obtain fused salt; under the condition of being communicated with inert gas, a molybdenum net is used as a cathode, a graphite rod is used as an anode, the molybdenum net is immersed in the fused salt, the graphite rod is inserted in the fused salt without touching the bottom, a stabilized power supply is communicated with the cathode and the anode electrode, and iron-containing small balls are prepared by electrolytic reduction; the obtained iron-containing small balls are pickled, suction filtered and vacuum dried to obtain micron pure iron powder. The iron-containing small balls are prepared for the first time, the maximum size can reach several centimeters, and the preparation by using the fused salt electrolytic method is short in process, low in energy consumption and friendly to the environment.

Description

TECHNICAL FIELD

[0001] The application relates to a method for reducing preparation of iron-containing small balls in a molten salt electrolytic cell and belongs to the technical field of non-ferrous metallurgy. BACKGROUND

[0002] The molten salt electrochemical method is a method for realizing electrolytic deoxidation of a cathode oxide in a solid state form to obtain a product by applying a certain cell voltage, using a molten salt as an electrolyte. Compared with other purification methods, the molten salt electrochemical method has the advantages of simple process, convenient operation, low investment cost, no special requirement for raw materials, high purity of obtained products, low impurity content, easy control of product morphology and the like, and embodies unique charm in the in-situ solid-state deoxidation of metal oxide to prepare metals and alloys.

[0003] Chinese patent CN110528029A discloses a method for preparing pure iron by a molten salt electrolysis method. In the method, NaCl and CaCl2 molten salts are mixed with Fe2O3, pure iron is obtained by molten salt electrolysis, and the pure iron is deposited on a nickel sheet and then collected to successfully prepare a pure iron plating layer. However, the problem is that the metals are difficult to collect on the current collector, and improper operation may even have residual current collectors. Therefore, the application provides a method for reducing preparation of iron-containing small balls in a molten salt electrolytic cell to solve the above problems. So far, there is no method for reducing preparation of iron-containing small balls in a molten salt electrolytic cell. SUMMARY

[0004] In view of the problems and deficiencies of the prior art, the application provides a method for reducing preparation of iron-containing small balls in a molten salt electrolytic cell. By applying a cell voltage of 2.6-2.8 V in the electrolyte of a MgCl2-xM molten salt system, electrolysis temperature is 750-850 DEG C, and the time is 3-6 h, iron-containing small balls are successfully prepared, the small balls have hard texture, high sphericity and good integrity, micron-level pure iron powder is obtained after simple acid washing, suction filtration and vacuum drying. The iron-containing small balls are prepared for the first time, the maximum size can reach several centimeters, the molten salt electrolysis method has the characteristics of short process, low energy consumption, environmental friendliness and easy collection of products, and greatly promotes the synthesis process of the molten salt electrolysis method for preparing metal powder materials.

[0005] The application is implemented through the following technical solutions.

[0006] A method for reducing preparation of iron-containing small balls in a molten salt electrolytic cell, and the specific steps are as follows:

[0007] Step 1, uniformly grinding and mixing alkali metal chlorides, and then putting the mixture into an alumina crucible to remove water in a vacuum drying box;

[0008] Step 2, the alumina crucible of step 1 is placed in the inner barrel of the inert gas resistance furnace, after heating and holding, micron Fe2O3 powder is added to completely mix with the molten salt to obtain the molten salt;

[0009] Step 3, under the condition of inert gas, molybdenum mesh is used as cathode and graphite rod is used as anode, the molybdenum mesh is immersed in the molten salt of step 2, the graphite rod is inserted in the molten salt of step 2 without touching the bottom, the constant voltage power supply is connected with the cathode and anode electrode, and the iron-containing small balls are prepared by electrolytic reduction;

[0010] Step 4, the iron-containing small balls obtained in step 3 are pickled, suction filtered and vacuum dried to obtain micron pure iron powder.

[0011] The alkali metal chloride molten salt in step 1 is MgCl2-xM, wherein M is one or a mixture of several arbitrary proportions of CaCl2, NaCl, BaCl2 and KCl, and x is the mass percentage of the molten salt M, and the value is 0-50%.

[0012] Step 1 is vacuum dried at a temperature of 80-120℃ for 12-24h.

[0013] The heating rate of the electrolytic furnace in step 2 is 2-10℃ / min, the electrolytic temperature is 750-850℃, and the holding time is 3-6h.

[0014] The amount of micron Fe2O3 powder added in step 2 is 0.01-0.5% of the total mass of the alkali metal chloride.

[0015] The voltage of the constant voltage power supply in step 3 is 2.6-2.8V.

[0016] In step 4, 1-5wt% HCl is used for pickling, and the pickling time is 0.5-1h; the vacuum drying temperature is 60-80℃.

[0017] In step 2, the micron Fe2O3 powder is replaced by copper oxide, manganese oxide, cobalt oxide, nickel oxide or chromium oxide to prepare corresponding metal small balls.

[0018] The molybdenum mesh in step 3 needs to be immersed in a beaker containing anhydrous ethanol and ultrasonically cleaned, the graphite rod needs to be washed with ultrapure water until no graphite powder residue is generated; the molybdenum mesh and the graphite rod need to be vacuum dried after cleaning, the vacuum drying temperature is 70℃, and the time is 0.5h.

[0019] The diameter of the iron-containing small balls in step 3 is 0.1-1.5cm, the small balls are hard, have high sphericity and good integrity.

[0020] The beneficial effects of the present application are:

[0021] 1. This invention uses Fe2O3, which is abundant and inexpensive, as a raw material, and the preparation process is short and energy consumption is low.

[0022] 2. The iron-containing microspheres prepared by this invention are formed in molten salt and do not deposit on the current collector. They do not need to be collected from the current collector through cumbersome steps, thus solving the problem of difficult collection of metals obtained by molten salt electrodeposition on the current collector.

[0023] 3. The iron-containing microspheres prepared by this invention are hard, have high sphericity and good integrity, breaking through the technical bottleneck that molten salt electrolysis of metal oxides can only obtain micro-nano-sized sponge-like powders; the iron-containing microspheres are simply acid washed, filtered and vacuum dried to obtain micron-sized pure iron powder. Attached Figure Description

[0024] Figure 1 This is Figure A, showing the actual operation of the reduction preparation process in Example 1 of the present invention;

[0025] Figure 2 This is Figure B, showing the actual operation of the reduction preparation process in Embodiment 1 of the present invention;

[0026] Figure 3 This is a macroscopic morphology diagram of the iron-containing microsphere composite material prepared in Example 1 of the present invention;

[0027] Figure 4 This is a macroscopic morphology diagram of the iron-containing microsphere composite material prepared in Example 2 of the present invention;

[0028] Figure 5 This is a macroscopic morphology diagram of the iron-containing microsphere composite material prepared in Example 3 of the present invention;

[0029] Figure 6 This is the XRD pattern of the iron-containing microsphere composite material prepared in Example 1 of this invention;

[0030] Figure 7 This is a SEM image of the iron-containing microsphere composite material prepared in Example 1 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] The specific steps of the method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell are as follows:

[0034] Step 1: Grind and mix 250g of alkali metal chloride molten salt evenly, then place it in an alumina crucible and remove moisture in a vacuum drying oven; the alkali metal chloride molten salt is MgCl2-xM, where M is a mixture of CaCl2 and NaCl in a mass ratio of 2:1, and x is the mass percentage of molten salt M, which is 1.5%. Weighing is performed in a glove box to avoid contamination from airborne impurities; vacuum dry at 80℃ for 24 hours.

[0035] Step 2: Place the alumina crucible from Step 1 under an inert gas atmosphere (argon, flow rate 150 mL / min). -1 In the inner liner of the resistance furnace, the temperature is raised to 850℃ at a rate of 2℃ / min and held for 6 hours. Then, micron-sized Fe2O3 powder is added and mixed with molten salt to obtain molten salt. The amount of micron-sized Fe2O3 powder added is 0.4% of the total mass of alkali metal chlorides. The micron-sized Fe2O3 powder is stirred with a molybdenum rod to make the molten salt completely mixed.

[0036] Step 3: Introduce inert gas (argon, flow rate 150 mL / min). -1 Under the following conditions, using a molybdenum mesh as the cathode and a graphite rod as the anode, the molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. A regulated power supply (2.8V) is connected to the cathode and anode electrodes, and iron-containing microspheres are prepared by electrolytic reduction; the actual operation diagram is shown below. Figure 1 and 2 As shown; the molybdenum mesh needs to be ultrasonically cleaned by immersing it in a beaker containing anhydrous ethanol, and the graphite rod needs to be rinsed with ultrapure water until no graphite powder residue is removed; after cleaning, the molybdenum mesh and graphite rod need to be vacuum dried at a temperature of 70℃ for 0.5 hours; in actual operation, the molybdenum mesh, graphite rod and molybdenum rod are connected by molybdenum wire to prepare the electrode, and the molybdenum rod acts as a conductor to carry electricity;

[0037] Step 4: The iron-containing microspheres obtained in Step 3 are acid-washed (using 1 wt% HCl for 0.5 h), filtered, and vacuum-dried (at 60 °C) to obtain micron-sized pure iron powder.

[0038] Macroscopic morphology images of the raw materials and the prepared iron-containing microspheres of this invention are shown below. Figure 3 As shown, from Figure 3 As can be seen from this, step 3 of the present invention can indeed prepare iron-containing microspheres, and the size of the iron-containing microspheres is about 1 cm.

[0039] The macroscopic morphology of the iron-containing microspheres prepared by this invention is shown in the figure below. Figure 3 As shown, the pellets were immersed in ultrapure water and allowed to stand for 24 hours after complete dissolution. The precipitate was then removed, filtered, and dried. The XRD pattern of the obtained product is shown below. Figure 6 As shown.

[0040] The SEM images (a, c) and EDS image (b) of the micron-sized pure iron powder prepared by this invention are as follows: Figure 7 As shown, the size of pure iron varies from 1μm to 20μm. Figure 7 (b) EDS surface scan analysis showed that the micron particles were mainly iron, indicating that Fe2O3 was reduced to Fe.

[0041] Example 2

[0042] The specific steps of the method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell are as follows:

[0043] Step 1: Grind and mix 250g of alkali metal chloride molten salt evenly, then place it in an alumina crucible and remove moisture in a vacuum drying oven; the alkali metal chloride molten salt is MgCl2-xM, where M is a mixture of CaCl2, NaCl and BaCl2 in a mass ratio of 5:3:2, and x is the mass percentage of molten salt M, which is 7.5%. Weighing is performed in a glove box to avoid contamination from air impurities; vacuum dry at 120℃ for 12h.

[0044] Step 2: Place the alumina crucible from Step 1 under an inert gas atmosphere (argon, flow rate 150 mL / min). -1 In the inner liner of the resistance furnace, the temperature is raised to 800℃ at a rate of 10℃ / min and held for 4 hours. Then, micron-sized Fe2O3 powder is added and mixed with molten salt to obtain molten salt. The amount of micron-sized Fe2O3 powder added is 0.2% of the total mass of alkali metal chloride. The micron-sized Fe2O3 powder is stirred with a molybdenum rod to make the molten salt completely mixed.

[0045] Step 3: Introduce inert gas (argon, flow rate 150 mL / min). -1 Under the following conditions, a molybdenum mesh is used as the cathode and a graphite rod as the anode. The molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. A regulated power supply (2.7V) is connected to the cathode and anode electrodes, and iron-containing microspheres are prepared by electrolytic reduction. The molybdenum mesh needs to be ultrasonically cleaned by immersing it in a beaker containing anhydrous ethanol, and the graphite rod needs to be rinsed with ultrapure water until no graphite powder residue is removed. After cleaning, the molybdenum mesh and graphite rod need to be vacuum dried at 70℃ for 0.5h. In actual operation, the molybdenum mesh and graphite rod are connected to the molybdenum rod with molybdenum wire to prepare the electrode, and the molybdenum rod acts as a conductor to carry current.

[0046] Step 4: Acid wash the iron-containing microspheres obtained in Step 3 (using 2wt% HCl, acid washing time is 1h), filter, and vacuum dry (vacuum drying temperature is 80℃) to obtain micron-sized pure iron powder.

[0047] Macroscopic morphology images of the raw materials and the prepared iron-containing microspheres of this invention are shown below. Figure 2 As shown, from Figure 2As can be seen from this, step 3 of the present invention can indeed prepare iron-containing microspheres, and the size of the iron-containing microspheres is about 0.75 cm.

[0048] Example 3

[0049] The specific steps of the method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell are as follows:

[0050] Step 1: Grind and mix 250g of alkali metal chloride molten salt evenly, then place it in an alumina crucible and remove moisture in a vacuum drying oven; the alkali metal chloride molten salt is MgCl2-xM, where M is KCl and x is the mass percentage of molten salt M, which is 1.5%. Weighing is performed in a glove box to avoid contamination from air impurities; vacuum dry at 120℃ for 12h.

[0051] Step 2: Place the alumina crucible from Step 1 under an inert gas atmosphere (argon, flow rate 150 mL / min). -1 In the inner liner of the resistance furnace, the temperature is raised to 750℃ at a rate of 6℃ / min and held for 2 hours. Then, micron-sized Fe2O3 powder is added and mixed with molten salt to obtain molten salt. The amount of micron-sized Fe2O3 powder added is 0.1% of the total mass of alkali metal chlorides. The micron-sized Fe2O3 powder is stirred with a molybdenum rod to make the molten salt completely mixed with the molten salt.

[0052] Step 3: Introduce inert gas (argon, flow rate 150 mL / min). -1 Under the following conditions, a molybdenum mesh is used as the cathode and a graphite rod as the anode. The molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. A regulated power supply (2.7V) is connected to the cathode and anode electrodes, and iron-containing microspheres are prepared by electrolytic reduction. The molybdenum mesh needs to be ultrasonically cleaned by immersing it in a beaker containing anhydrous ethanol, and the graphite rod needs to be rinsed with ultrapure water until no graphite powder residue is removed. After cleaning, the molybdenum mesh and graphite rod need to be vacuum dried at 70℃ for 0.5h. In actual operation, the molybdenum mesh and graphite rod are connected to the molybdenum rod with molybdenum wire to prepare the electrode, and the molybdenum rod acts as a conductor to carry current.

[0053] Step 4: The iron-containing microspheres obtained in Step 3 are acid-washed (using 4wt% HCl for 0.8h), filtered, and vacuum-dried (at 70℃) to obtain micron-sized pure iron powder.

[0054] Example 4

[0055] The specific steps of the method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell are as follows:

[0056] Step 1: Grind and mix 250g of alkali metal chloride molten salt evenly and place it in an alumina crucible. Remove moisture in a vacuum drying oven. The alkali metal chloride molten salt is MgCl2-xM, where M is NaCl and x is the mass percentage of molten salt M, which is 10%. Weighing is performed in a glove box to avoid contamination from airborne impurities. Vacuum dry at 120℃ for 12 hours.

[0057] Step 2: Place the alumina crucible from Step 1 under an inert gas atmosphere (argon, flow rate 150 mL / min). -1 In the inner liner of the resistance furnace, the temperature is raised to 750℃ at a rate of 6℃ / min and held for 2 hours. Then, micron-sized copper oxide powder is added and mixed with molten salt to obtain molten salt. The amount of micron-sized copper oxide powder added is 0.8% of the total mass of alkali metal chloride. The micron-sized copper oxide powder is stirred with a molybdenum rod to make the molten salt completely mixed.

[0058] Step 3: Introduce inert gas (argon, flow rate 150 mL / min). -1 Under the following conditions, a molybdenum mesh is used as the cathode and a graphite rod as the anode. The molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. A regulated power supply is connected to the cathode and anode electrodes, and copper-containing microspheres are prepared by electrolytic reduction. The molybdenum mesh needs to be ultrasonically cleaned by immersing it in a beaker containing anhydrous ethanol, and the graphite rod needs to be rinsed with ultrapure water until no graphite powder residue is removed. After cleaning, the molybdenum mesh and graphite rod need to be vacuum dried at 70°C for 0.5 hours. In actual operation, the molybdenum mesh and graphite rod are connected to the molybdenum rod with molybdenum wire to prepare the electrode, and the molybdenum rod acts as a conductor to carry current.

[0059] Step 4: Acid wash (using 4wt% HCl, acid washing time is 0.8h) of the copper-containing microspheres obtained in Step 3, filter, and vacuum dry (vacuum drying temperature is 70℃) to obtain micron-sized pure copper powder.

[0060] Example 5

[0061] The specific steps of the method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell are as follows:

[0062] Step 1: Grind and mix 250g of alkali metal chloride molten salt evenly, then place it in an alumina crucible and remove moisture in a vacuum drying oven; the alkali metal chloride molten salt is MgCl2-xM, where M is BaCl2 and x is the mass percentage of molten salt M, which is 8%; weighing is performed in a glove box to avoid contamination from air impurities; vacuum dry at 120℃ for 12h.

[0063] Step 2: Place the alumina crucible from Step 1 under an inert gas atmosphere (argon, flow rate 150 mL / min). -1In the inner liner of the resistance furnace, the temperature is raised to 750℃ at a rate of 6℃ / min and held for 2 hours. Then, micron-sized cobalt oxide powder (other metal oxides) is added and mixed thoroughly with molten salt to obtain molten salt. The amount of micron-sized cobalt oxide powder added is 0.9% of the total mass of alkali metal chlorides. The powder is stirred with a molybdenum rod to make the powder and molten salt completely mixed.

[0064] Step 3: Introduce inert gas (argon, flow rate 150 mL / min). -1 Under the following conditions, a molybdenum mesh is used as the cathode and a graphite rod as the anode. The molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. A regulated power supply is connected to the cathode and anode electrodes, and cobalt-containing microspheres are prepared by electrolytic reduction. The molybdenum mesh needs to be ultrasonically cleaned by immersing it in a beaker containing anhydrous ethanol, and the graphite rod needs to be rinsed with ultrapure water until no graphite powder residue is removed. After cleaning, the molybdenum mesh and graphite rod need to be vacuum dried at a temperature of 70°C for 0.5 hours. In actual operation, the molybdenum mesh and graphite rod are connected to the molybdenum rod with molybdenum wire to prepare the electrode, and the molybdenum rod acts as a conductor to carry current.

[0065] Step 4: Acid wash (using 4wt% HCl, acid washing time is 0.8h) of the cobalt-containing microspheres obtained in Step 3, filter, and vacuum dry (vacuum drying temperature is 70℃) to obtain micron-sized pure cobalt powder.

[0066] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell, characterized in that... The specific steps are as follows: Step 1: Grind and mix the alkali metal chloride molten salt evenly, then place it in an alumina crucible and remove moisture in a vacuum drying oven; Step 2: Place the alumina crucible from Step 1 into the inner liner of an inert gas-filled resistance furnace, heat and hold it at that temperature, then add micron-sized Fe2O3 powder and mix it thoroughly with the molten salt to obtain the molten salt. Step 3: Under the condition of introducing inert gas, with a molybdenum mesh as the cathode and a graphite rod as the anode, the molybdenum mesh is immersed in the molten salt of step 2, and the graphite rod is inserted into the molten salt of step 2 without touching the bottom. The regulated power supply is connected to the cathode and anode electrodes, and iron-containing microspheres are prepared by electrolytic reduction. Step 4: Acid wash, filter and vacuum dry the iron-containing microspheres obtained in Step 3 to obtain micron-sized pure iron powder; In step 1, the alkali metal chloride molten salt is MgCl2-xM, where M is one or more of CaCl2, NaCl, BaCl2, and KCl in any proportion, and x is the mass percentage of molten salt M, which ranges from 1.5% to 50%. In step 3, the voltage of the regulated power supply slot is 2.6~2.8V.

2. The method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell according to claim 1, characterized in that: Step 1 involves vacuum drying at a temperature of 80~120℃ for 12~24 hours.

3. The method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell according to claim 1, characterized in that: In step 2, the heating rate of the electrolytic furnace is 2~10℃ / min, the temperature is raised to the electrolysis temperature of 750℃~850℃, and the holding time is 3~6h.

4. The method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell according to claim 1, characterized in that: In step 2, the amount of micron-sized Fe2O3 powder added is 0.01~0.5% of the total mass of alkali metal chlorides.

5. The method for preparing iron-containing microspheres by reduction in a molten salt electrolytic cell according to claim 1, characterized in that: In step 4, the pickling process uses 1-5 wt% HCl for 0.5-1 h; the vacuum drying temperature is 60-80℃.

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