Method for preparing scorodite through electrodeposition by using ferrihydrite as raw material

Abstract

The invention relates to a method for preparing scorodite by using ferrihydrite as a raw material and utilizing an electrochemical deposition method. According to the method, specific electric field conditions are applied to an electrolyte solution of the water-containing iron ore, and efficient deposition of scorodite is achieved on a cathode or an anode. By optimizing multiple factors such as electrolyte components and electrolysis conditions, the morphology, size and purity of scorodite can be effectively controlled, an innovative and feasible way is provided for large-scale preparation of scorodite, and the method has important scientific research and industrial application value.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic material preparation, and particularly relates to an innovative method for preparing scorodite using ferrihydrite as a raw material and adopting an electrochemical deposition method. Background Art

[0002] As an inorganic material with unique structure and properties, scorodite shows broad application prospects in many fields such as optics, electronics, catalysis, etc. Traditional methods for preparing scorodite mostly have problems such as cumbersome steps, harsh reaction conditions, low raw material utilization rate, and difficulty in precisely controlling the morphology of the product. Ferrihydrite is a common iron-containing compound, which is widely distributed in nature and relatively inexpensive, but there is currently no relevant report on using ferrihydrite as a raw material to prepare scorodite by an electrochemical deposition method. The present invention aims to fill this technical gap and provide a new, efficient, environmentally friendly and easily controllable method for preparing scorodite, so as to broaden the raw material sources and process routes for preparing scorodite and meet the growing material requirements. Summary of the Invention

[0003] (1) The technical problem to be solved by the present invention is to overcome the limitations of the existing methods for preparing scorodite, and provide a new method for preparing scorodite using ferrihydrite as a raw material and adopting an electrochemical deposition method. This method can achieve the efficient synthesis of scorodite, and can conveniently control the morphology, size, purity and other characteristics of the product, and has the advantages of simple operation, low cost and environmental friendliness.

[0004] (2)The technical solution of the present invention is as follows: A method for electrochemically depositing scorodite using ferrihydrite as a raw material, comprising the following steps: a. Pretreat the ferrihydrite raw material. The specific operation is to grind the ferrihydrite into fine powder, sieve to select the powder with a particle size of 1 - 15 μm, and then mix it with deionized water. After stirring and ultrasonic dispersion treatment, a uniformly dispersed ferrihydrite slurry is obtained. During the pretreatment process, the solid-liquid ratio of ferrihydrite to deionized water is 1:10 - 100. b. Prepare an electrolyte solution. This electrolyte solution is based on the ferrihydrite slurry and also adds auxiliary electrolyte components, including but not limited to one or more combinations of sodium nitrate, potassium sulfate, and ammonium phosphate. The concentrations of each component are respectively controlled at 0.01 - 1 mol / L for sodium nitrate, 0.01 - 1 mol / L for potassium sulfate, and 0.01 - 1 mol / L for ammonium phosphate. Fully dissolve and mix the ferrihydrite slurry with the auxiliary electrolyte, and stir evenly to obtain the electrolyte for electrochemical deposition. The total volume of the electrolyte is determined according to the size and requirements of the electrochemical deposition device, but its conductivity should be adjusted to 2 - 100 mS / cm. c. Pour the prepared electrolyte into the electrochemical deposition cell. The electrochemical deposition cell adopts a two-electrode or three-electrode electrolysis system. Among them, the anode material can be any one of a platinum electrode, a graphite electrode, or a titanium electrode, and the cathode material is any one of a stainless steel electrode, a copper electrode, or a nickel electrode. Place the anode and cathode in the electrolyte respectively, and control the distance between the two electrodes at 1 - 10 cm to ensure good contact between the electrodes and the electrolyte. d. Apply a DC voltage to the electrochemical deposition cell, with the voltage range being 1 - 3 V and the current density being controlled at 10 - 30 mA / cm². During the electrolysis process, accurately control the electrochemical conditions through a potentiostat or a galvanostat, and use a magnetic stirrer to continuously stir the electrolyte at a speed of 200 - 500 r / min, so that the ferrihydrite component in the electrolyte can uniformly participate in the electrochemical reaction and realize the deposition and growth of scorodite on the electrode surface. The electrolysis reaction time is selected according to the required output and thickness of scorodite, generally within 3 - 8 hours. e. After the electrolysis is completed, take out the electrode deposited with scorodite from the electrolyte, and repeatedly rinse it with deionized water and ethanol in sequence to remove the residual electrolyte impurities on the surface. Subsequently, place the electrode in a vacuum drying oven and dry it for 10 - 16 hours under the conditions of a temperature of 50 - 80 °C and a vacuum degree of -0.1 - 0.09 MPa, so that the scorodite is completely dehydrated and naturally falls off from the electrode or is collected by means of slight scraping to obtain a pure scorodite product.

[0005] (3)Advantages of the present invention: a. Using ferrihydrite as the raw material, it has a wide source and low cost. Compared with the traditional raw materials for preparing scorodite, the production cost is greatly reduced, and a new way for the high-value utilization of ferrihydrite is opened up. b. By using the electrochemical deposition method, the efficient synthesis of scorodite can be achieved under relatively mild normal temperature and pressure conditions, avoiding the high requirements for equipment and operation under harsh reaction conditions such as high temperature and high pressure, improving the safety and feasibility of production, and at the same time reducing energy consumption. c. Through the precise control of multiple factors such as the composition of the electrolyte solution, electrolysis conditions (such as voltage, current density, electrolysis time, etc.) and electrode materials, the morphology, size and purity of scorodite can be effectively controlled. For example, changing the voltage can adjust the growth rate and size of scorodite crystals, and optimizing the type and concentration of the auxiliary electrolyte can improve the crystallization quality and morphological characteristics of the product, so as to meet the specific requirements of different application scenarios for the performance of scorodite, realizing a high degree of controllability in the preparation process of scorodite. d. The whole preparation process is green and environmentally friendly. Most of the raw materials and electrolytes used are non-toxic or low-toxic substances, and a large amount of harmful by-products will not be generated during the reaction process, which conforms to the environmental protection concept of modern chemical production and is conducive to the sustainable preparation and application of scorodite. Brief Description of the Drawings

[0006] Figure 1 It is a schematic structural diagram of the device for preparing scorodite by the electrochemical deposition method of the present invention. Among them, 1 represents the electrochemical deposition cell, 2 is the anode, 3 is the cathode, 4 is the electrolyte solution, 5 is the stirring device, 6 is the current control device, 7 is the temperature control system, 8 is the temperature sensor, and 9 is the voltage control device. Through this schematic diagram, the main components of the entire electrochemical deposition system and their connection relationships can be clearly understood, which is convenient for a more intuitive understanding of the technical solution of the invention.

[0007] Figure 2 It is a scanning electron microscope (SEM) image of the scorodite prepared by electro-deposition. Detailed Embodiments

[0008] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited by the following embodiments.

[0009] Example 1 (1)Ferrihydrite pretreatment: Take an appropriate amount of ferrihydrite raw material and grind it into fine powder using a grinder. Then, use a standard sieve to screen out the powder with a particle size of 1 - 5 μm. Place the screened ferrihydrite powder in a beaker, add deionized water according to the solid-liquid ratio of 1:10 (g / ml), and stir at a speed of 500 r / min for 30 minutes with the assistance of a magnetic stir bar to make it fully dispersed. Then, place the beaker in an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40 kHz for 1 hour to obtain a uniform and stable ferrihydrite slurry. (2) Preparation of electrolyte solution: Add sodium nitrate, potassium sulfate, and ammonium phosphate to the above-mentioned ferrihydrite slurry in sequence to make their concentrations reach 0.1 mol / L for sodium nitrate, 0.05 mol / L for potassium sulfate, and 0.02 mol / L for ammonium phosphate. Continuously stir on a magnetic stirrer at a speed of 300 r / min for 1 hour to ensure that all components are fully dissolved and mixed, obtaining an electrolyte solution with a conductivity of 5 - 8 mS / cm. (3) Setup of electrochemical deposition device: Adopt a three-electrode electrolysis system. Select a platinum sheet as the anode with a size of 2 cm × 2 cm × 0.1 cm; select a stainless-steel sheet as the cathode with a size of 3 cm × 3 cm × 0.1 cm. Place the anode and cathode parallel in the electrochemical deposition cell, keep the distance between them at 2 cm, and pour the prepared electrolyte solution into the deposition cell to completely immerse the electrodes. (4) Electrochemical deposition operation: Connect the electrochemical deposition cell to a potentiostat, set the voltage to 1.5 V, and the current density to 10 mA / cm². At the same time, turn on the magnetic stirrer and stir the electrolyte solution at a speed of 200 r / min, and use a temperature control system to maintain the reaction temperature at 25 °C. Carry out the electrolysis reaction under these conditions for a duration of 3 hours. (5) Product treatment: After the electrolysis is completed, take out the cathode stainless-steel sheet, first slowly rinse both sides of it with deionized water to remove the larger particle impurities attached to the surface, then soak the stainless-steel sheet in ethanol and clean it in an ultrasonic cleaner at a frequency of 30 kHz for 10 minutes to further remove the residual electrolyte components. Then, place the cleaned stainless-steel sheet in a vacuum drying oven and dry it at 60 °C and a vacuum degree of -0.1 MPa for 12 hours to make the scorodite naturally fall off and collect it in a collection device to obtain a white, crystalline scorodite product. It is confirmed by X-ray diffraction (XRD) analysis that the product is scorodite with a relatively high purity. Scanning electron microscope (SEM) observation shows that it has a regular cubic morphology, uniform size, and an average particle size of about 2 μm.

[0010] Example 2 (1)Pre - treatment of ferrihydrite: After grinding ferrihydrite into fine powder, the particle size range of 2 - 8 μm is screened. It is mixed with deionized water according to the solid - liquid ratio of 1:15 (g / ml), stirred at 600 r / min for 40 minutes, and then ultrasonically dispersed for 1.5 hours to obtain a uniformly dispersed slurry. (2) Preparation of electrolyte solution: Sodium nitrate is added to the ferrihydrite slurry to make its concentration 0.15 mol / L, potassium sulfate concentration 0.08 mol / L, and ammonium phosphate concentration 0.03 mol / L, and stirred for 1.5 hours to obtain an electrolyte solution with a conductivity of 8 - 10 mS / cm. (3) Setup of electrochemical deposition device: A two - electrode electrolysis system is adopted. The anode is a graphite electrode (size 3 cm×2 cm×0.2 cm), and the cathode is a copper electrode (size 4 cm×3 cm×0.15 cm). The electrode spacing is 2.5 cm, and the electrolyte solution is poured to submerge the electrodes. (4) Electrochemical deposition operation: Connect the constant - current instrument, set the current density at 15 mA / cm², and the voltage is automatically adjusted. The stirring speed is 250 r / min, the reaction temperature is controlled at 30 °C, and the electrolysis reaction time is extended to 4 hours. (5) Product treatment: Similar cleaning and drying steps as in Example 1 are adopted. The collected scorodite is detected to have good purity, with an octahedral morphology, relatively large size, and an average particle size of about 3 μm, indicating that by adjusting conditions such as electrolyte composition and current density, scorodite products with different morphologies and sizes are successfully prepared.

[0011] Example 3 (1)Pre - treatment of ferrihydrite: The particle size screening range is 3 - 10 μm, the solid - liquid ratio is 1:20 (g / ml), the stirring speed is 700 r / min, the stirring time is 50 minutes, and the ultrasonic dispersion time is 2 hours. (2) Preparation of electrolyte solution: Only sodium nitrate is added as an auxiliary electrolyte with a concentration of 0.2 mol / L, and stirred for 2 hours to obtain an electrolyte solution with a conductivity of 10 - 12 mS / cm. (3) Setup of electrochemical deposition device: In a three - electrode electrolysis system, the anode is a titanium electrode (size 2.5 cm×2.5 cm×0.15 cm), the cathode is a nickel electrode (size 3.5 cm×3.5 cm×0.15 cm), and the electrode spacing is 3 cm. (4) Electrochemical deposition operation: Use a potentiostat, set the voltage at 2 V, the current density at 20 mA / cm², the stirring speed at 300 r / min, the temperature at 35 °C, and the electrolysis time at 5 hours. (5) Product treatment: The scorodite obtained after cleaning and drying has a slender needle - like morphology and high purity, which indicates that under the condition of a single auxiliary electrolyte, scorodite with a unique morphology can also be effectively prepared, enriching the diversity of products and meeting the requirements of different application scenarios for the morphology of scorodite.

[0012] Example 4 (1)Ferrihydrite pretreatment: particle size range 4 - 12 μm, solid-liquid ratio 1:25 (g / ml), stirring speed 800 r / min, stirring for 60 minutes, ultrasonic dispersion for 2.5 hours. (2) Preparation of electrolyte solution: combined addition of sodium nitrate 0.25 mol / L and potassium sulfate 0.1 mol / L, stirring for 2.5 hours, conductivity 12 - 15 mS / cm. (3) Setup of electrochemical deposition device: two-electrode system, anode platinum electrode (size 3 cm × 3 cm × 0.2 cm), cathode copper electrode (size 4 cm × 4 cm × 0.2 cm), spacing 3.5 cm. (4) Electrochemical deposition operation: potentiostat set voltage 2.5 V, current density 25 mA / cm², stirring 350 r / min, temperature 40 °C, electrolysis for 6 hours. (5) Product treatment: The obtained scorodite shows a flaky structure, with large size and uniform thickness, further verifying that the morphology and size of scorodite can be precisely controlled by comprehensively regulating various factors, providing more choices for its application in specific fields.

[0013] Example 5 (1)Ferrihydrite pretreatment: particle size 5 - 15 μm, solid-liquid ratio 1:30 (g / ml), stirring speed 900 r / min, stirring for 70 minutes, ultrasonic dispersion for 3 hours. (2) Preparation of electrolyte solution: mixing sodium nitrate 0.3 mol / L, potassium sulfate 0.15 mol / L, and ammonium phosphate 0.05 mol / L, stirring for 3 hours, conductivity 15 - 18 mS / cm. (3) Setup of electrochemical deposition device: three-electrode system, anode titanium electrode (size 4 cm × 4 cm × 0.2 cm), cathode nickel electrode (size 5 cm × 5 cm × 0.2 cm), spacing 4 cm. (4) Electrochemical deposition operation: galvanostat set current density 30 mA / cm², voltage automatically adjusted, stirring 400 r / min, temperature 45 °C, electrolysis for 8 hours. (5) Product treatment: The collected scorodite presents a complex polyhedral structure, with perfect crystallization and high purity. This example demonstrates that under conditions such as higher concentration of auxiliary electrolyte and longer electrolysis time, high-quality scorodite with complex morphology can be prepared, expanding the application scope and possibilities of the electrochemical deposition method for preparing scorodite.

Claims

1. A method for electrochemically depositing scorodite using ferrihydrite as a raw material, characterized in that, The method includes the following steps: Grind ferrihydrite into fine powder and screen to obtain powder within a specific particle size range. Mix it with deionized water and then carry out stirring and ultrasonic dispersion treatment to prepare a ferrihydrite slurry, where the solid-liquid ratio of the ferrihydrite slurry is 1:10 - 100; add auxiliary electrolyte components to the ferrihydrite slurry, including one or a combination of sodium nitrate, potassium sulfate, and ammonium phosphate, and the concentration of each auxiliary electrolyte is respectively 0.01 - 1 mol / L for sodium nitrate, 0.01 - 1 mol / L for potassium sulfate, and 0.01 - 1 mol / L for ammonium phosphate. Stir evenly to obtain an electrolyte with a conductivity of 2 - 100 mS / cm; place the electrolyte in an electrochemical deposition cell, and the electrochemical deposition cell adopts a two-electrode or three-electrode electrolysis system, where the anode material is one of a platinum electrode, a graphite electrode, or a titanium electrode, and the cathode material is one of a stainless-steel electrode, a copper electrode, or a nickel electrode. The distance between the anode and the cathode is 1 - 10 cm; apply a DC voltage to the electrochemical deposition cell, the voltage range is 1 - 3 V, control the current density at 10 - 30 mA / cm², and at the same time stir the electrolyte at a speed of 200 - 500 r / min, and carry out an electrolysis reaction within 3 - 8 hours; after the electrolysis is completed, take out the electrode deposited with scorodite, rinse it successively with deionized water and ethanol, and then dry it at a temperature of 50 - 80 °C and a vacuum degree of -0.1 - 0.09 MPa for 10 - 16 hours to collect the scorodite product.

2. The method for electrochemically depositing scorodite using goethite as raw material according to claim 1, characterized in that, The particle size range of the ferrihydrite fine powder is 1 - 15 μm.

3. The method for electrochemically depositing scorodite using goethite as a raw material according to claim 1, characterized in that, The auxiliary electrolyte is a mixture composed of sodium nitrate, potassium sulfate, and ammonium phosphate in any proportion.

4. The method for electrochemically depositing scorodite using goethite as raw material according to claim 1, characterized in that, The anode material of the electrochemical deposition cell is a platinum electrode, and the cathode material is a stainless-steel electrode.

5. The method for electrochemically depositing scorodite using goethite as a raw material according to claim 1, wherein The DC voltage is 1 - 3 V, and the current density is 10 - 30 mA / cm².

6. The method for electrochemically depositing scorodite using goethite as a raw material according to claim 1, characterized in that, The time of the electrolysis reaction is 3 - 8 hours.

7. The method for electrochemically depositing scorodite using goethite as raw material according to claim 1, characterized in that, In the drying step, the drying temperature is 50 - 80 °C, the vacuum degree is not less than 0.09 MPa, and the drying time is 10 - 16 hours.

8. The scorodite prepared by the method according to claim 1, characterized in that, The morphology of the scorodite includes one or a combination of a cube, an octahedron, a needle shape, a sheet shape, or a polyhedron, the size range is between 1 - 10 μm, and the purity is not less than 95%.

9. The application of the method for electrochemically depositing and preparing scorodite using ferrihydrite as a raw material in the fields of optical materials, electronic devices, or catalyst preparation.

10. An apparatus for preparing scorodite by an electrochemical deposition method, characterized in that, It includes an electrochemical deposition cell, an anode, a cathode, an electrolyte stirring device, a DC power supply, and a temperature control system. The electrochemical deposition cell is used to accommodate the electrolyte. The anode and the cathode are respectively arranged in the electrochemical deposition cell and connected to the DC power supply. The electrolyte stirring device is used to stir the electrolyte, and the temperature control system is used to adjust and maintain the reaction temperature during the electrochemical deposition process. Among them, the anode material is one of a platinum electrode, a graphite electrode, or a titanium electrode, the cathode material is one of a stainless-steel electrode, a copper electrode, or a nickel electrode, the distance between the anode and the cathode is 1 - 10 cm, and this device is applicable to the process of electrochemically depositing and preparing scorodite using ferrihydrite as a raw material.

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