Preparation method and application of composite ferrite loaded magnetic calcium sulfate whisker
By preparing magnetic calcium sulfate whiskers supported by composite ferrite, the problems of heavy metal ion recovery from electroplating wastewater and carbonyl sulfide removal from gas were solved, achieving efficient and environmentally friendly heavy metal conversion and gas purification, which is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU CHANGHUAN ENVIRONMENTAL TECH CO LTD
- Filing Date
- 2025-02-28
- Publication Date
- 2026-07-31
AI Technical Summary
Existing technologies are insufficient to effectively recover heavy metal ions from electroplating wastewater and convert them into solid chemicals, while avoiding the generation of toxic waste and new pollution. Furthermore, they are inefficient at removing carbonyl sulfides from gases.
By preparing magnetic calcium sulfate whiskers supported on composite ferrite, heavy metal ions in electroplating wastewater are converted into solid chemicals, and their catalytic activity is used to remove carbonyl sulfide in the gas. During the process, crystal seeds are added to assist crystallization and avoid agglomeration. The magnetic properties are used to achieve rapid separation.
It achieves efficient recovery and conversion of heavy metal ions, avoids the generation of toxic waste, reduces operating costs, is suitable for industrial-scale production, and improves the removal efficiency of carbonyl sulfur in gas.
Smart Images
Figure CN119869437B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing and applying magnetic calcium sulfate whiskers supported on composite ferrite, belonging to the field of heavy metal recycling technology. Background Technology
[0002] Electroplating wastewater refers to all wastewater generated in the electroplating workshop during the electroplating production process. Depending on the required functions and properties of the electroplated products, the production processes vary, resulting in complex types and qualities of wastewater with difficult-to-control composition. The wastewater often contains heavy metal ions such as chromium, cadmium, nickel, copper, and lead. Therefore, to facilitate subsequent wastewater treatment, it is usually separated into different pipelines and treated separately. Electroplating wastewater is further classified into those primarily containing heavy metals, such as nickel-containing wastewater, copper-containing wastewater, chromium-containing wastewater, etc. The treatment and disposal of electroplating wastewater has become an urgent problem to be solved in the industry.
[0003] Heavy metal recovery is an important component of sustainable development and environmental protection goals. Various recovery technologies have been developed, including adsorption, precipitation, ion exchange, solvent extraction, membrane separation, electrochemical methods, and microbiological approaches. These methods can effectively recover heavy metals from wastewater; however, previous studies have also shown that most methods still have drawbacks, such as generating complex and diverse metal sludge, residual toxic waste, or causing new pollution. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing and applying magnetic calcium sulfate whiskers supported on composite ferrite. This method can directly convert heavy metal ions in electroplating wastewater into solid chemicals without generating toxic waste or causing new pollution. The obtained solid chemicals can also effectively remove carbonyl sulfide from the gas.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing magnetic calcium sulfate whiskers supported by composite ferrite involves pretreating electroplating wastewater with ferrous sulfate, then adding iron oxide nanoparticles, mixing and stirring, adding calcium oxide, aging, and then separating the solid and liquid and drying to obtain magnetic calcium sulfate whiskers supported by composite ferrite nanoparticles.
[0007] Among them, electroplating wastewater contains Cr 6+ Cr 3+ In addition, it also contains Ni 2+ Cu 2+ Mn 2+ Fe 2+ Fe 3+ At least one of them.
[0008] Preferably, the electroplating wastewater contains Cr 6+ Cr 3+ Ni 2+ Cu 2+ Mn 2+ Fe 2+ and Fe 3+ ;
[0009] Among them, Fe 2+ Fe 3+ Ni 2+ Cu 2+ Mn 2+ Cr 3+ Cr 6+ The concentrations were 200–2000 mg / L, 500–4000 mg / L, 300–3000 mg / L, 10–5000 mg / L, 5–1000 mg / L, 100–10000 mg / L, and 400–8000 mg / L, respectively.
[0010] Preferably, the specific method of pretreatment is as follows: ferrous sulfate heptahydrate is added to the electroplating wastewater and stirred for 40-80 minutes;
[0011] Among them, ferrous sulfate heptahydrate and Cr in electroplating wastewater 6+ The molar ratio is (5-30):1.
[0012] Preferably, the amount of iron(III) oxide nanoparticles added is 2-6 times the metal content in the electroplating wastewater.
[0013] Preferably, the particle size of the iron oxide nanoparticles is 20 nm to 1 mm.
[0014] Preferably, the pH of the solution after adding calcium oxide is 7-12.
[0015] Preferably, the aging conditions are: room temperature, 0.5-5 hours.
[0016] Preferably, the drying conditions are: 60-100℃, 3-10h.
[0017] The application of composite ferrite-supported magnetic calcium sulfate whiskers prepared by any of the above methods in gas purification is to remove carbonyl sulfide contained in the gas.
[0018] The beneficial effects of this invention are as follows:
[0019] Seed-assisted crystallization is a form of "heteroepitaxy." Heterogeneous surfaces can act as nuclei and provide active sites, thus making nucleation energy-favorable, altering crystallization behavior, and accelerating the crystallization process. Adding crystal seeds during crystal synthesis can increase the crystallization rate and inhibit the formation of unwanted phases, resulting in a product selectivity effect. This can lead to localized supersaturation of low-concentration solutions through adsorption or other mechanisms, thereby inducing crystallization. This invention uses seed-induced crystallization to form calcium sulfate whiskers, providing a loading carrier for composite ferrite nanoparticles. Simultaneously, it disperses the composite ferrite nanoparticles, reducing aggregation and laying the foundation for improved removal of carbonyl sulfides.
[0020] Magnetic calcium sulfate whiskers supported on composite ferrite exhibit catalytic activity, converting carbonyl sulfide into easily processed products through oxidation or hydrolysis. The high specific surface area of calcium sulfate whiskers provides abundant adsorption sites, enhancing the enrichment of carbonyl sulfide and the efficiency of the catalytic reaction. The combination of ferrite and calcium sulfate whiskers enhances chemical stability and tolerance to complex environments. The magnetic properties of the material allow for rapid separation and recovery via an external magnetic field after the reaction, avoiding the high costs of traditional adsorbent filtration or centrifugation, making it suitable for continuous processing.
[0021] Meanwhile, this method is simple to operate, environmentally friendly, has low energy consumption and raw material costs, good economic benefits, is conducive to large-scale industrial production, and has good prospects for industrial application. Attached Figure Description
[0022] Figure 1 This is a SEM image of the magnetic calcium sulfate whisker precipitate of the composite ferrite nanoparticles obtained in Example 1.
[0023] Figure 2 The image shows the XRD pattern of the magnetic calcium sulfate whisker precipitate of the composite ferrite nanoparticles obtained in Example 1. Detailed Implementation
[0024] Example 1
[0025] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+After stirring for 60 min, 3 g of 20 nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 10, and then aged at room temperature for 2 h. Centrifugation yielded a solid precipitate and supernatant. The solid precipitate was dried at 80 °C for 6 h and then ground to obtain magnetic calcium sulfate whisker precipitate with composite ferrite nanoparticles loaded on its surface. Its SEM and XRD patterns are shown below. Figure 1 , 2 As shown.
[0026] Depend on Figure 1 The left side shows that the calcium sulfate whiskers exhibit a fibrous structure with uniform diameter and ferrite nanoparticles attached to their surface. The right side shows that the ferrite particles attached to the calcium sulfate whiskers are relatively uniform in size and have regular, nearly spherical shapes; the particle surfaces are relatively smooth, with only slight agglomeration between some particles.
[0027] Depend on Figure 2 Characteristic diffraction peaks of both calcium sulfate and ferrite phases can be clearly observed. The diffraction peaks of the two phases are independent, indicating that calcium sulfate and ferrite phases coexist in the product. The diffraction peaks of calcium sulfate mainly correspond to typical crystal planes (020), (021), and (041) in its crystal structure, indicating the presence of a well-crystallized calcium sulfate phase in the sample. At the same time, the characteristic diffraction peaks of ferrite are also clearly visible, with peak positions corresponding to crystal planes (311), (220), and (400) of the spinel structure. The sharp peak shapes indicate that the ferrite nanoparticles have good crystallinity.
[0028] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 99.2%, 99.9%, 99.9%, and 99.5%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat toxic carbonyl sulfide gas at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 93% after 300 minutes.
[0029] Example 2
[0030] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+In a 60-minute stirring process, 3g of 20nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 7, and then aged at room temperature for 2 hours. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80℃ for 6 hours and then ground to obtain magnetic calcium sulfate whiskers with composite ferrite nanoparticles loaded on the surface.
[0031] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 98.1%, 99.7%, 80.2%, and 93.8%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 86% after 300 minutes.
[0032] Example 3
[0033] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ In a solution of iron oxide (Fe3O4) and stirred for 60 min, 3 g of 20 nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 8, and then aged at room temperature for 2 h. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80 °C for 6 h and then ground to obtain magnetic calcium sulfate whiskers with composite ferrite nanoparticles loaded on the surface.
[0034] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 98.5%, 99.6%, 99.3%, and 96.5%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 88% after 300 minutes.
[0035] Example 4
[0036] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ In a solution of iron oxide (Fe3O4) and stirred for 60 min, 3 g of 20 nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 9, and the solution was aged at room temperature for 2 h. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80 °C for 6 h and then ground to obtain magnetic calcium sulfate whiskers with composite ferrite nanoparticles loaded on the surface.
[0037] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 99.1%, 99.5%, 99.3%, and 97.8%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 91% after 300 minutes.
[0038] Example 5
[0039] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ In a solution of iron oxide (Fe3O4) seeds, after stirring for 60 min, 3 g of 20 nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 11, and then aged at room temperature for 2 h. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80 °C for 6 h and then ground to obtain magnetic calcium sulfate whiskers with composite ferrite nanoparticles loaded on the surface.
[0040] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 99.2%, 99.5%, 99.1%, and 98.5%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 90% after 300 minutes.
[0041] Example 6
[0042] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ In a solution of iron oxide (Fe3O4) and stirred for 60 min, 3 g of 20 nm iron oxide seed crystals were added. CaO was added while stirring to adjust the pH to 12, and then aged at room temperature for 2 h. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80 °C for 6 h and then ground to obtain magnetic calcium sulfate whiskers with composite ferrite nanoparticles loaded on the surface.
[0043] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 99.2%, 99.7%, 99.1%, and 98.9%, respectively. Magnetic calcium sulfate whiskers with surface-loaded composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the equilibrium gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, after 300 minutes, the removal efficiency of carbonyl sulfur was 92%.
[0044] Comparative Example 1
[0045] It is basically the same as Example 1, except that CaO was not added to adjust the pH in Comparative Example 1.
[0046] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ After stirring for 60 minutes, 3g of ferric oxide seed crystals with a particle size of 20nm were added, and then aged at room temperature for 2 hours. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80℃ for 6 hours and then ground to obtain composite ferrite nanoparticles.
[0047] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 87.5%, 85.6%, 75.8%, and 86.8%, respectively. Composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the balance gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 80% after 300 minutes.
[0048] Comparative Example 2
[0049] It is basically the same as Example 1, except that no iron oxide seeds were added in Comparative Example 2 and no CaO was added to adjust the pH.
[0050] Add 4.46g of ferrous sulfate heptahydrate to 100ml of electroplating wastewater (containing 1000mg / L Cr). 6+ 1000mg / L Fe 2 + 2000mg / L Fe 3+ 1500mg / L Ni 2+ 800mg / L Cu 2+ and 3000 mg / L Cr 3+ After stirring for 60 minutes, the mixture was aged at room temperature for 2 hours. Centrifugation was performed to obtain a solid precipitate and a supernatant. The solid precipitate was dried at 80°C for 6 hours and then ground to obtain composite ferrite nanoparticles.
[0051] The removal rates of Cr, Fe, Ni, and Cu in electroplating wastewater were 78.6%, 80.2%, 70.2%, and 85.2%, respectively. Composite ferrite nanoparticles were used to treat the toxic gas carbonyl sulfide at a concentration of 500 ppm, with nitrogen as the balance gas and a reaction space velocity of 15000 h⁻¹. -1 The reaction temperature was 150℃, the water vapor content was 10%, and the packing amount in the hydrolysis tower was 3% of the tower height. Under the above conditions, the removal efficiency of carbonyl sulfur was 75% after 300 minutes.
[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing magnetic calcium sulfate whiskers supported on composite ferrite, characterized in that, The process involves pretreating electroplating wastewater with ferrous sulfate, then adding iron oxide nanoparticles, stirring, adding calcium oxide, aging, and finally separating the solid and liquid, drying, and grinding to obtain magnetic calcium sulfate whiskers loaded with composite ferrite nanoparticles. Among them, electroplating wastewater contains Cr 6+ Cr 3+ In addition, it also contains Ni 2+ Cu 2+ Mn 2+ Fe 2+ Fe 3+ At least one of them.
2. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, Electroplating wastewater contains Cr 6+ Cr 3+ Ni 2+ Cu 2+ Mn 2+ Fe 2+ and Fe 3+ ; Among them, Fe 2+ Fe 3+ Ni 2+ Cu 2+ Mn 2+ Cr 3+ Cr 6+ The concentrations were 200–2000 mg / L, 500–4000 mg / L, 300–3000 mg / L, 10–5000 mg / L, 5–1000 mg / L, 100–10000 mg / L, and 400–8000 mg / L, respectively.
3. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The specific method for pretreatment is as follows: ferrous sulfate heptahydrate is added to the electroplating wastewater and stirred for 40-80 minutes; Among them, ferrous sulfate heptahydrate and Cr in electroplating wastewater 6+ The molar ratio is (5-30):
1.
4. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The amount of iron oxide nanoparticles added is 2-6 times the metal content in the electroplating wastewater.
5. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The particle size of the iron oxide nanoparticles is 20 nm to 1 mm.
6. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The pH of the solution after adding calcium oxide is 7-12.
7. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The aging conditions are: room temperature, 0.5-5 hours.
8. The method for preparing magnetic calcium sulfate whiskers supported on composite ferrite according to claim 1, characterized in that, The drying conditions are: 60-100℃, 3-10h.
9. The application of the composite ferrite-supported magnetic calcium sulfate whiskers prepared by the method according to any one of claims 1-8 in gas purification, characterized in that, It is used to remove carbonyl sulfides from gases.