A method for preparing beta-FeOOH nanocrystals based on silicate minerals

Abstract

The application discloses a method for preparing beta-FeOOH nanocrystals based on silicate minerals, which comprises the following steps: (1) mixing silicate mineral powder with FeCl3 solution, and obtaining a turbid liquid containing beta-FeOOH and SiO2 after reaction; solid-liquid separation is performed to obtain solid substances; the reaction temperature is 20-50 DEG C, and the reaction time is 48-120 h; (2) mixing the solid substances obtained in step (1) with NaOH solution; after sufficient stirring, solid-liquid separation is performed, an equal amount of NaOH solution is added to the solid substances after solid-liquid separation, and stirring is continued; after stirring, solid-liquid separation is performed; the solid substances after solid-liquid separation are cleaned and dried to obtain beta-FeOOH nanoparticles. The beta-FeOOH prepared by the method of the application is of nanometer scale and uniform particle size without adding additional crystal form regulators or surfactants, and the resource utilization of silicate minerals is realized.

Description

Technical Field

[0001] This invention relates to a method for preparing β-FeOOH nanocrystals based on silicate minerals. Background Technology

[0002] Silicate minerals are the most widely distributed, diverse, and abundant group of minerals in the Earth's crust. Typical examples include wollastonite, olivine, and serpentine, which are rich in calcium (Ca) and magnesium (Mg) ions. Some of these silicate minerals are used in building materials and cement raw materials, while most are disposed of as tailings in tailings ponds. Therefore, large quantities of Ca / Mg-based silicate minerals ultimately accumulate in construction waste, industrial solid waste, and tailings storage systems, resulting in resource waste and environmental problems such as groundwater pollution, tailings instability, and soil salinization due to long-term accumulation.

[0003] β-FeOOH possesses stable chemical properties, high specific surface area, and a unique tunnel structure, making it widely used in new energy battery precursors, high-efficiency water treatment adsorbents, and photocatalysts. However, traditional methods for preparing β-FeOOH (such as FeCl3 forced hydrolysis, hydrothermal methods, and microemulsion methods) consume large amounts of thermal energy and alkaline materials, and the size of nanoscale particles is difficult to control. To obtain uniform nanoscale particles, these methods require the addition of crystal form regulators to the system, resulting in cumbersome processes, low economic efficiency, and difficulty in mass production. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing β-FeOOH nanocrystals based on silicate minerals, wherein the method uses Ca / Mg-based silicate minerals as OH... - The release agent and β-FeOOH nucleating seed crystals have enabled the production of β-FeOOH nanocrystals with uniform particle size without the addition of additional crystal form regulators. On the other hand, they have also enabled the resource utilization of Ca / Mg-based silicate minerals.

[0005] Technical solution: The method for preparing β-FeOOH nanocrystals based on silicate minerals according to the present invention includes the following steps:

[0006] (1) Preparation of β-FeOOH: Ca / Mg based silicate minerals (with the nanocrystals grown in situ to be uniform in size by slow release of hydroxide ions) were dried and ground to obtain silicate mineral powder. The silicate mineral powder was mixed with FeCl3 solution and reacted fully to obtain a mixed solution containing β-FeOOH and SiO2. Solid-liquid separation was performed to obtain a clear solution rich in Ca / Mg ions and a mixed precipitate rich in β-FeOOH and SiO2. The mixed precipitate was washed twice by centrifugation with deionized water and dried to obtain a yellow powder.

[0007] (2) Separation and purification of β-FeOOH: The mixed precipitate obtained in step (1) was mixed with NaOH solution; the mixture was stirred thoroughly to dissolve SiO2. After stirring, the solid-liquid separation was performed using a centrifuge. The supernatant was then discarded, and an equal amount of NaOH solution was added to the solid repeatedly. Stirring was continued, and after stirring, the solid-liquid separation was performed using a centrifuge. The solid was then washed once with deionized water. After drying the product, β-FeOOH nanoparticles with high purity and good crystallinity were obtained.

[0008] In step (1), the Ca / Mg-based silicate mineral powder has a particle size of 200 mesh; the FeCl3 solution has a concentration of 0.02~0.05 mol / L, and the molar ratio of Ca / Mg-based silicate mineral to FeCl3 is 15:0.4~1. The temperature during the stirring process is 20~50℃, and the stirring time is 48~120h, preferably 25~40℃. Solid-liquid separation is performed using a centrifuge at a speed of 8000~10000 rpm for 5~10min.

[0009] In step (2), the concentration of the NaOH solution is 1.5~2.5 mol / L, and the solid-liquid ratio of the mixed precipitate to the NaOH solution is 0.1~0.2 g / 30~50 mL, preferably 0.15 g / 40 mL; the stirring temperature is 25~35℃, and the stirring time is 4~8 h, preferably 30℃, and the stirring time is 6 h. After the first addition of NaOH solution, the centrifugation speed is 3000~4000 r / min, and the centrifugation time is 1~2 min; after the second addition of NaOH solution, the centrifugation speed is 4000~6000 rpm, preferably 5000 rpm, and the centrifugation time is 3~5 min.

[0010] This invention utilizes Fe in FeCl3 solution 3+ The multi-stage hydrolysis characteristics, through the release of H + Dissolving silicate minerals; during this slow dissolution process, H + OH is continuously consumed, prompting - Slow release from the mineral surface; simultaneously, the silicate mineral surface is negatively charged, and the exposed Si-O - The site is Fe 3+ It provides excellent adsorption sites; therefore, a higher local supersaturation is formed at the solid-liquid interface, promoting the interfacial nucleation and growth of β-FeOOH nanocrystals on the silicate mineral surface, accompanied by Ca... 2+ / Mg 2+ The process involves leaching and the formation of SiO2 precipitate. Then, utilizing the dissolving power of NaOH for SiO2, SiO2 is converted into soluble SiO3. 2-Sodium silicate is introduced into the solution, and finally, high-purity (close to 100% purity) β-FeOOH nanocrystals are obtained by centrifugation.

[0011] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention realizes the resource utilization of Ca / Mg based silicate minerals, on the one hand by extracting Ca from the minerals. 2+ Mg 2+ (1) Provide metal ions for carbonization and storage, and simultaneously prepare β-FeOOH nanocrystals, realizing the transformation of silicate minerals into high-value-added products; (2) The β-FeOOH prepared by the method of the present invention is nanoscale and has uniform particle size without the addition of additional crystal form regulators or surfactants. Attached Figure Description

[0012] Figure 1 The image shows the XRD pattern of the β-FeOOH nanocrystals obtained in Example 1.

[0013] Figure 2 Here is a SEM image of the β-FeOOH nanocrystals obtained in Example 1;

[0014] Figure 3 This is a particle size distribution diagram of the β-FeOOH nanocrystals obtained in Example 1;

[0015] Figure 4 The image shows the XRD pattern of the β-FeOOH nanocrystals obtained in Example 2.

[0016] Figure 5 Here is a SEM image of the β-FeOOH nanocrystals obtained in Example 2;

[0017] Figure 6 The image shows the XRD pattern of the β-FeOOH nanocrystals obtained in Example 3.

[0018] Figure 7 This is a SEM image of the β-FeOOH nanocrystals obtained in Example 3. Detailed Implementation

[0019] Example 1

[0020] This invention relates to a method for preparing β-FeOOH nanocrystals based on silicate minerals, comprising the following steps:

[0021] (1) Preparation of β-FeOOH: Wollastonite (CaSiO3) was dried and ground to obtain 200-mesh wollastonite powder. 0.015 mol of wollastonite powder was mixed evenly with 20 mL of FeCl3 solution with a concentration of 0.05 mol / L. The mixture was stirred at 25 °C for 96 h until the wollastonite was completely dissolved. After stirring, the mixture was shaken and transferred to a 50 mL centrifuge tube. The solid and liquid were separated by centrifuging at 10000 r / min for 5 min to obtain a clear liquid rich in Ca ions and a mixed precipitate rich in β-FeOOH and SiO2. The mixed precipitate was washed twice by centrifugation with deionized water and dried at 60 °C for 12 h in a forced-air drying oven to obtain a yellow powder.

[0022] (2) Separation and purification of β-FeOOH: 0.15g of yellow powder obtained in step (1) was added to 40mL of NaOH solution with a concentration of 2.5mol / L. The mixture was stirred at 30℃ for 6h using a constant temperature magnetic stirrer. After stirring, the mixture was shaken and transferred to a 50mL centrifuge tube. The centrifuge was used at a speed of 3000r / min and centrifuged for 1min. The solid obtained by centrifugation was then added to 40mL of NaOH solution with a concentration of 2.5mol / L and stirred at 30℃ for 6h. After stirring, the solid and liquid were separated by centrifugation at a speed of 5000r / min and centrifuged for 3min. The solid obtained was washed with deionized water and then placed in a forced-air drying oven and dried at 60℃ for 12h to obtain brown β-FeOOH powder.

[0023] pass Figure 1 It can be seen that the β-FeOOH nanocrystals prepared in Example 1 have high purity (no other impurity peaks in XRD) and good crystal quality; the spindle-shaped particles are intact and without defects in the SEM image. Figure 2 It can be seen that the β-FeOOH nanocrystals prepared in Example 1 have uniform particle size, and further... Figure 3 The particle size distribution diagram confirms that the β-FeOOH nanocrystals prepared in Example 1 have uniform particle size.

[0024] Example 2

[0025] This invention relates to a method for preparing β-FeOOH nanocrystals based on silicate minerals, comprising the following steps:

[0026] (1) Preparation of β-FeOOH: Wollastonite (CaSiO3) was dried and ground to obtain 200-mesh wollastonite powder. 0.015 mol of wollastonite powder was mixed evenly with 20 mL of FeCl3 solution with a concentration of 0.05 mol / L. The mixture was stirred at 40 °C for 48 h with a constant temperature magnetic stirrer until the wollastonite was completely dissolved. After stirring, the mixture was shaken and transferred to a 50 mL centrifuge tube. The solid and liquid were separated by centrifugation at 10000 r / min for 5 min to obtain a clear liquid rich in Ca ions and a mixed precipitate rich in β-FeOOH and SiO2. The mixed precipitate was washed twice by centrifugation with deionized water and dried at 60 °C for 12 h in a forced-air drying oven to obtain a yellow powder.

[0027] (2) Separation and purification of β-FeOOH: 0.15g of yellow powder obtained in step (1) was added to 40mL of NaOH solution with a concentration of 2.5mol / L. The mixture was stirred at 30℃ for 6h using a constant temperature magnetic stirrer. After stirring, the mixture was shaken and transferred to a 50mL centrifuge tube. The centrifuge was used at a speed of 3000r / min and centrifuged for 1min. The solid obtained by centrifugation was then added to 40mL of NaOH solution with a concentration of 2.5mol / L and stirred at 30℃ for 6h. After stirring, the solid and liquid were separated by centrifugation at a speed of 5000r / min and centrifuged for 3min. The solid obtained was washed with deionized water and then placed in a forced-air drying oven and dried at 60℃ for 12h to obtain brown β-FeOOH powder.

[0028] pass Figure 4 It can be seen that the β-FeOOH nanocrystals prepared in Example 2 have high purity and no other impurity peaks. Through... Figure 5 It can be seen that the β-FeOOH nanocrystals prepared in Example 2 have a relatively uniform particle size.

[0029] Example 3

[0030] This invention relates to a method for preparing β-FeOOH nanocrystals based on silicate minerals, comprising the following steps:

[0031] (1) Preparation of β-FeOOH: 200-mesh forsterite (Mg2SiO4) was dried and ground. 0.015 mol of forsterite powder was mixed with 20 mL of 0.02 mol / L FeCl3 solution. The mixture was stirred at 40 °C for 48 h with a constant temperature magnetic stirrer until the forsterite was completely dissolved. After stirring, the mixture was shaken and transferred to a 50 mL centrifuge tube. The solid and liquid were separated by centrifugation at 10000 r / min for 5 min to obtain a clear liquid rich in Ca ions and a mixed precipitate rich in β-FeOOH and SiO2. The mixed precipitate was washed twice with deionized water by centrifugation and dried at 60 °C for 12 h in a forced-air drying oven to obtain a yellow powder.

[0032] (2) Separation and purification of β-FeOOH: 0.15g of yellow powder obtained in step (1) was added to 40mL of NaOH solution with a concentration of 2.5mol / L. The mixture was stirred at 30℃ for 6h using a constant temperature magnetic stirrer. After stirring, the mixture was shaken and transferred to a 50mL centrifuge tube. The centrifuge was used at a speed of 3000r / min and centrifuged for 1min. The solid obtained by centrifugation was then added to 40mL of NaOH solution with a concentration of 2.5mol / L and stirred at 30℃ for 6h. After stirring, the solid and liquid were separated by centrifugation at a speed of 5000r / min and centrifuged for 3min. The solid obtained was washed with deionized water and then placed in a forced-air drying oven and dried at 60℃ for 12h to obtain brown β-FeOOH powder.

[0033] pass Figure 6 It can be seen that the β-FeOOH nanocrystals prepared in Example 3 have high purity and no other impurity peaks. Through... Figure 7 It can be seen that the β-FeOOH nanocrystals prepared in Example 3 have a relatively uniform particle size.

[0034] Table 1 shows the size and morphology of the β-FeOOH nanocrystals obtained in Examples 1-3.

[0035]

[0036] The method of this invention utilizes OH groups on the surface of silicate minerals. - The slow release properties and Fe 3+ Multi-stage hydrolysis capability, through H + The dissolution of silicate minerals induces the exposure of Si-O on their surface. - The active site, which is active for Fe 3+ It has excellent adsorption properties, which is conducive to the heterogeneous nucleation and dispersion of β-FeOOH, thereby promoting the formation of β-FeOOH nanocrystals with uniform particle size.

Claims

1. A method for preparing β-FeOOH nanocrystals based on silicate minerals, characterized in that, Includes the following steps: (1) Silicate mineral powder is mixed with FeCl3 solution and reacted fully to obtain a turbid liquid containing β-FeOOH and SiO2; solid-liquid separation is performed to obtain a solid; the reaction temperature is 20~50℃ and the reaction time is 48~120h; (2) Mix the solid obtained in step (1) with NaOH solution; stir thoroughly, and after stirring, the solid and liquid are separated. Add an equal amount of NaOH solution to the solid after solid-liquid separation, continue stirring, and after stirring, the solid and liquid are separated. Wash and dry the solid after solid-liquid separation to obtain β-FeOOH nanoparticles.

2. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (1), the particle size of the Ca / Mg-based silicate mineral powder is 200 mesh.

3. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (1), the Ca / Mg-based silicate mineral is wollastonite or forsterite.

4. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (1), the concentration of the FeCl3 solution is 0.02~0.05mol / L, and the molar ratio of the Ca / Mg-based silicate mineral powder to FeCl3 is 15:0.4~1.

5. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (1), a centrifuge is used for solid-liquid separation. The centrifugation speed is 8000~10000 rpm and the time is 5~10 min.

6. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (2), the concentration of the NaOH solution is 1.5~2.5mol / L, and the solid-liquid ratio of the mixed precipitate to the NaOH solution is 0.1~0.2g / 30~50mL.

7. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (2), the stirring temperature is 25~35℃ and the stirring time is 4~8h.

8. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (2), a centrifuge is used for solid-liquid separation. After the first addition of NaOH solution, the centrifugation speed is 3000~4000 r / min and the centrifugation time is 1~2 min. After the second addition of NaOH solution, the centrifugation speed is 4000~6000 rpm and the centrifugation time is 3~5 min.

9. The method for preparing β-FeOOH nanocrystals based on silicate minerals according to claim 1, characterized in that: In step (2), the β-FeOOH nanoparticles are spindle-shaped with a major diameter of 65~141nm and a minor diameter of 15~38nm.

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