Method for preparing sodium hexafluoroferrite from industrial production waste liquid
Through dynamic pH control, photocatalytic reaction and gradient drying technology, the problems of low purity and high cost in the resource utilization of fluorine-containing waste liquid and iron waste liquid were solved, and efficient synthesis of sodium hexafluoroferrate was achieved, which was used as raw materials for new energy batteries, reducing production costs and eliminating environmental risks.
Patent Information
- Application Number
- CN202510833766.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-09-12
AI Technical Summary
In the existing technology, the resource utilization of fluorine-containing waste liquid and iron waste liquid has problems such as poor fluoride ion selectivity, serious heavy metal interference and low reaction efficiency, resulting in low purity and high cost of sodium hexafluoroferrate product.
Sodium hexafluoroferrate is separated and synthesized through dynamic pH control, photocatalytic reaction and gradient drying technology, combined with a rolled nanofiltration membrane and a horizontal spiral centrifuge, including ultraviolet light catalysis of the TiO2/graphene composite catalytic layer and fluidized bed drying, to achieve efficient separation and purification.
The method achieves efficient separation of sodium hexafluoroferrate, reduces production costs, eliminates environmental risks, and utilizes waste liquid resources. The synthesis time is short and the energy consumption is low, and the product can be used as a raw material for new energy batteries.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of resource recovery, in particular to a method for preparing sodium hexafluoroferrate by utilizing industrial production waste liquid. Background Art
[0002] Fluorine-containing waste liquid (containing hydrofluoric acid, fluoride, etc.) generated in industrial production processes such as chip manufacturing and iron-based waste liquid (containing Fe 3+ , sulfates, etc.) are all high-risk pollutants. Traditional treatment methods involve neutralization and concentration followed by landfill, which not only wastes fluorine and iron resources but also poses the risk of heavy metal leakage. Currently, the synthesis of sodium hexafluoroferrate relies on high-purity sodium fluoride and iron salts, which is expensive. If calcium salts are used to precipitate fluorine, calcium sulfate will also be produced, forming a mixed precipitate with no use value. The resource utilization of fluorine-containing waste liquids also faces the following problems:
[0003] Poor fluoride ion selectivity: F in wastewater - With Cl - 、SO4 2- The coexistence of competitive anions makes it difficult to enrich efficiently; heavy metal interference is serious: Al 3+ 、Cu 2+ Other impurities and Fe 3+ Competitive coordination leads to low product purity; low reaction efficiency: the traditional precipitation method produces coarse and uneven grains and requires long aging time. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for preparing sodium hexafluoroferrate using industrial waste liquid, so as to solve the problems existing in the resource utilization process of the above-mentioned fluorine-containing waste liquid.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] The present invention relates to a method for preparing sodium hexafluoroferrate using industrial waste liquid, comprising the following steps:
[0007] Step 1: Collect fluorine-containing waste liquid and iron-containing waste liquid generated from the industrial production process respectively; add sulfuric acid to adjust the pH to 3.5-5.5, stir and filter to remove Fe(OH)2 colloidal precipitation and insoluble impurities, then add NaOH solution to the clear liquid, adjust the pH to 8.5-10.0, filter through a roll nanofiltration membrane to separate heavy metal precipitates such as Cu(OH)2 and Ni(OH)2, and obtain the cleaned clear liquid F - concentrate;
[0008] Step 2: Go to F - Add Fe to the concentrate 3+ Make F - :Fe 3+Reach 5:1 to 6:1, and use photocatalytic reaction to synthesize sodium hexafluoroferrate to generate Na3FeF6 suspension;
[0009] Step 3: Use a horizontal spiral centrifuge to separate the Na3FeF6 solid, and the separated mother liquor is recycled;
[0010] Step 4: The Na3FeF6 solid wet material is subjected to fluidized bed gradient drying to obtain the finished sodium hexafluoroferrate.
[0011] In step 1 of the above method, the operating pressure of the rolled nanofiltration membrane is 2.5 MPa.
[0012] In step 1 of the above method, the waste liquid generated in the industrial production process includes fluorine-containing waste liquid generated from the chip cleaning process and iron etching waste liquid generated from the chip etching process.
[0013] In step 2 of the above method, the photocatalytic reaction is catalyzed by ultraviolet light of the TiO2 / graphene composite catalytic layer and reacts at a temperature of 60°C for 30 to 40 minutes to generate a Na3FeF6 suspension.
[0014] In step 4 of the above method, gradient drying includes pre-drying and finishing drying; pre-drying uses a pneumatic drying tower to remove surface moisture with hot air at 50°C; finishing drying uses a fluidized bed to dry at 80-120°C with zoned temperature control.
[0015] The beneficial effects of the present invention are:
[0016] The present invention synergistically treats fluorine-containing waste liquid and iron waste liquid generated during industrial production, separating sodium hexafluoroferrate from the fluorine-containing waste liquid through dynamic pH control and photothermal catalytic reaction. The present invention is simple to operate, has a short synthesis time, and low energy consumption. The product can be used as a raw material for new energy batteries, turning waste into treasure, achieving a resource-based circular economy, eliminating the environmental risks associated with landfilling hazardous waste, and significantly reducing the production cost of sodium hexafluoroferrate. DETAILED DESCRIPTION
[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0018] Example 1
[0019] The present invention relates to a method for preparing sodium hexafluoroferrate by utilizing industrial production waste liquid, comprising the following steps:
[0020] Step 1: Collaborative collection of waste liquids from multiple sources. Collect fluorine-containing waste liquids from the chip cleaning process, as well as other fluorine-containing waste liquids produced by other fluorine-containing production processes. The main components are HF, NaF, Na2SO4, NaCL and trace amounts of Al 3+ 、Cu 2+ 、Ni 2+ Collect iron etching waste liquid and ferric chloride or ferric sulfate generated in industrial production, press F - :Fe 3+ The mixture is prepared in a molar ratio of 6:1 to form a mixed solution. If it is insufficient, add ferric chloride or ferric sulfate.
[0021] Then, dynamic pH gradient is used to control the impurities. The first stage of acid precipitation: slowly add 10% dilute sulfuric acid to the mixture, adjust the pH to 3.5, and stir for 30 minutes to make Al 3+ Fe(OH)2 colloid precipitate is formed first and filtered out. Second stage alkaline precipitation: continue to add 20% NaOH solution, adjust the pH to 8.5, generate Cu(OH)2 and Ni(OH)2 precipitate, separate by spiral nanofiltration membrane, and measure the filtrate F - Cu in concentrate 2+ Residue <5ppm.
[0022] Step 2: Photocatalytic synthesis of sodium hexafluoroferrate using a photocatalytic reactor. The photocatalytic reactor uses a titanium alloy inner shell, an outer wall with an integrated wavelength of 365nm and a power density of 50mW / cm 2 The UV LED array is coated with a 50 μm thick TiO2 / graphene composite catalyst layer on the inner wall. 3+ Keep F - :Fe 3+ The ratio is 6:1. When it is insufficient, FeCl3 waste liquid is added to optimize the reaction conditions.
[0023] Reaction process:
[0024] Stage 1: Turn on the UV light source and keep it at 60℃ for 30min to promote Fe 3+ Hydrolysis and F - coordination; stage 2 dynamic microwave irradiation, heating to 80 ° C and maintaining for 90 minutes to accelerate the growth of crystal nuclei; the total reaction time is 1.5 hours, and a white microcrystalline Na3FeF6 suspension is generated.
[0025] Step 3: Solid-liquid separation and closed-loop recycling of mother liquor
[0026] The horizontal spiral centrifuge with a speed of 4000rpm and a differential speed ratio of 1:20 is used to separate the solid and liquid. The moisture content of the wet material is ≤15%. The mother liquor is treated and reused by electrodialysis desalination. The mother liquor enters the anion and cation exchange membrane group. The fresh water after electrodialysis contains Na +The concentrated water with NaCl content less than 50ppm is used for molecular sieve regeneration, and the concentrated water with NaCl content greater than or equal to 15% is returned to step 1 and recycled as a neutralizing agent.
[0027] Step 4: fluidized bed gradient drying.
[0028] The wet material enters the air drying tower through a screw conveyor, and the surface moisture is quickly removed by hot air at a speed of 8m / s at 50℃, reducing the moisture content to 5-8%.
[0029] Fluidized bed fine drying uses zoned temperature control. Zone one is set at 80°C to fluidize and preheat the material to prevent crystal bursting; zone two is set at 100°C to remove bound water; and zone three is set at 120°C for deep dehydration, achieving a final moisture content of less than 0.5%. The purity of the Na3FeF6 was determined to be 99.5%.
[0030] Example 2
[0031] Step 1: Collect fluorine-containing waste liquid and ferric chloride or ferric sulfate waste liquid from other industrial production, press F - :Fe 3+ The mixture is prepared in a molar ratio of 5:1 to form a mixed solution. If it is insufficient, add ferric chloride or ferric sulfate.
[0032] Slowly add 10% dilute sulfuric acid to the mixture to adjust the pH to 5.5 and stir for 30 minutes to make Al 3+ Fe(OH)2 colloid precipitate is formed first and removed by filtration. Second stage alkaline precipitation: continue to add 20% NaOH solution and adjust the pH to 10.0 to generate Cu(OH)2 and Ni(OH)2 precipitates, which are separated by spiral nanofiltration membrane.
[0033] Step 2: Photocatalytically synthesize sodium hexafluoroferrate using a photocatalytic reactor. At the same time, Fe 3+ Keep F - :Fe 3+ The ratio is 5:1.
[0034] Step 3: solid-liquid separation and closed-loop recycling of mother liquor are the same as in Example 1.
[0035] Step 4: Fluidized bed gradient drying is used as in Example 1.
[0036] The purity of the prepared Na3FeF6 was determined to be 99.8%.
[0037] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.
Claims
1. A method for preparing sodium hexafluoroferrate using industrial waste liquid, characterized in that: The steps include: Step 1: Separately collect fluorine-containing waste liquid and iron-containing waste liquid generated from the industrial production process; add sulfuric acid to adjust the pH to 3.5-5.5, stir and filter to remove Fe(OH)2 colloidal precipitate and insoluble impurities, then add NaOH solution to the clear liquid, adjust the pH to 8.5-10.0, filter through a spiral nanofiltration membrane to separate heavy metal precipitates such as Cu(OH)2 and Ni(OH)2, and obtain a clear liquid after impurity removal; Step 2: Add Fe to F-concentrate 3+ Make F - :Fe 3+ Reach 5:1 to 6:1, and use photocatalytic reaction to synthesize sodium hexafluoroferrate to generate Na3FeF6 suspension; Step 3: Use a horizontal spiral centrifuge to separate the Na3FeF6 solid, and the separated mother liquor is recycled; Step 4: The Na3FeF6 solid wet material is subjected to fluidized bed gradient drying to obtain the finished sodium hexafluoroferrate.
2. The method for preparing sodium hexafluoroferrate using industrial waste liquid according to claim 1, wherein In step 1, the operating pressure of the rolled nanofiltration membrane is 2.5 MPa.
3. The method for preparing sodium hexafluoroferrate using industrial waste liquid according to claim 1, wherein In step 1, the waste liquid generated in the industrial production process includes fluorine-containing waste liquid generated from the chip cleaning process and iron etching waste liquid generated from the chip etching process.
4. The method for preparing sodium hexafluoroferrate using industrial waste liquid according to claim 1, wherein In step 2, the photocatalytic reaction is catalyzed by ultraviolet light of the TiO2 / graphene composite catalytic layer and reacts at a temperature of 60°C for 30 to 40 minutes to generate a Na3FeF6 suspension.
5. The method for preparing sodium hexafluoroferrate using industrial waste liquid according to claim 1, characterized in that: In step 4, gradient drying includes pre-drying and finishing drying; pre-drying uses a pneumatic drying tower to remove surface moisture with hot air at 50°C; finishing drying uses a fluidized bed with zoned temperature control at 80-120°C.