Cobalt ferrite, method for preparing the same, and use thereof

Abstract

This invention provides cobalt ferrite, its preparation method, and its application, belonging to the field of water treatment technology. The preparation method provided by this invention includes the following steps: (1) mixing cobalt salt, iron salt, and water to obtain a mixed solution; (2) mixing the mixed solution obtained in step (1) with an alkaline solution and carrying out a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155–165°C. This invention uses cobalt salt and iron salt as raw materials to prepare cobalt ferrite through a hydrothermal reaction. By controlling the temperature of the hydrothermal reaction, the obtained cobalt ferrite also contains iron(III) oxide (Fe3O4). The interaction between the two results in a faster removal rate of the prepared cobalt ferrite when used for pollutant removal in water, allowing for pollutant degradation in a shorter time. The results of the examples show that when the cobalt ferrite prepared by this invention is used to remove bisphenol A from water, its removal rate reaches nearly 100% within 5 minutes.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to cobalt ferrite, its preparation method, and its application. Background Technology

[0002] With the development of the pharmaceutical and cleaning industries, the production and use of pharmaceutical and personal care products (PPCPs) have increased rapidly, resulting in their residues in water bodies. These residual PPCPs may have potential adverse effects on human and animal health, therefore, it is necessary to remove PPCPs from water bodies.

[0003] Currently, the main methods for removing PPCPs from water bodies include biological, physical, and chemical methods. Traditional biological treatment processes have limited effectiveness in removing PPCPs, require long treatment times, and the wastewater is prone to discoloration and odor changes. Therefore, they are usually combined with other methods for PPCP removal from various types of wastewater. Physical methods for treating PPCPs do not alter the chemical structure of the pollutants, and there is still a risk of migration and transformation after removal. Advanced oxidation technologies (AEOs) within chemical methods are considered a promising way to degrade pollutants, but these methods require suitable external conditions to activate the oxidant. Although existing technologies use cobalt ferrite to activate oxidants for pollutant removal in water, the removal rate and time are relatively slow when using cobalt ferrite in water. Summary of the Invention

[0004] The purpose of this invention is to provide cobalt ferrite, its preparation method, and its applications. The cobalt ferrite prepared by the method provided by this invention exhibits rapid removal rates and short removal times when used to remove pollutants from water.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing cobalt ferrite, comprising the following steps:

[0007] (1) Mix cobalt salt, iron salt and water to obtain a mixed solution;

[0008] (2) The mixed solution obtained in step (1) is mixed with an alkaline solution and subjected to a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165℃.

[0009] Preferably, the molar ratio of cobalt ions in the cobalt salt to iron ions in the iron salt in step (1) is 1:(1.9 to 2.1).

[0010] Preferably, in step (1), the mass ratio of cobalt salt to water is (1.4-1.5) g: 60 mL.

[0011] Preferably, the pH value of the mixed solution and the alkali solution in step (2) is 11 to 12.

[0012] Preferably, the hydrothermal reaction time in step (2) is 11 to 13 hours.

[0013] The present invention also provides cobalt ferrite prepared by the preparation method described in the above technical solution.

[0014] The present invention also provides the application of cobalt ferrite as described above in the removal of pharmaceuticals or personal care products from water.

[0015] Preferably, the water to be treated is mixed with cobalt ferrite and an oxidant for degradation to obtain purified water.

[0016] Preferably, the mass ratio of cobalt ferrite to the volume ratio of the water to be treated is (0.1-0.5) g: 1 L.

[0017] Preferably, after the water to be treated is mixed with cobalt ferrite and oxidant, the concentration of the oxidant is 0.1 to 0.3 mmol / L.

[0018] This invention provides a method for preparing cobalt ferrite, comprising the following steps: (1) mixing cobalt salt, iron salt, and water to obtain a mixed solution; (2) mixing the mixed solution obtained in step (1) with an alkaline solution and carrying out a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165℃. This invention uses cobalt salt and iron salt as raw materials to prepare cobalt ferrite through a hydrothermal reaction. By controlling the temperature of the hydrothermal reaction, the obtained cobalt ferrite also contains iron(III) oxide (Fe3O4). The interaction between the two results in a faster removal rate of the prepared cobalt ferrite when used for pollutant removal in water, allowing for pollutant degradation in a shorter time. The results of the examples show that when the cobalt ferrite prepared according to this invention is used to remove bisphenol A from water, its removal rate reaches nearly 100% within 5 minutes. Attached Figure Description

[0019] Figure 1 A schematic diagram illustrating the mechanism of PPCP degradation in water using cobalt ferrite;

[0020] Figure 2 SEM image of cobalt ferrite prepared in Example 1 at a scale of 500 nm;

[0021] Figure 3 This is a SEM image of cobalt ferrite prepared in Example 1 at the 1 μm scale;

[0022] Figure 4 The XRD pattern of cobalt ferrite prepared in Example 1;

[0023] Figure 5The removal rates of bisphenol A in Application Examples 1-3 and Comparative Application Example 1 are compared.

[0024] Figure 6 The removal rates of bisphenol A in application examples 1, 4-6 and comparative application example 2 are shown.

[0025] Figure 7 The removal rates of bisphenol A in Application Example 1 and Comparative Application Example 3 are shown. Detailed Implementation

[0026] This invention provides a method for preparing cobalt ferrite, comprising the following steps:

[0027] (1) Mix cobalt salt, iron salt and water to obtain a mixed solution;

[0028] (2) The mixed solution obtained in step (1) is mixed with an alkaline solution and subjected to a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165℃.

[0029] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.

[0030] This invention involves mixing cobalt salt, iron salt, and water to obtain a mixed solution.

[0031] In this invention, the cobalt salt is preferably Co(NO3)2·6H2O.

[0032] In this invention, the iron salt is preferably Fe(NO3)3·9H2O.

[0033] In this invention, the water is preferably deionized water.

[0034] In this invention, the molar ratio of cobalt ions in the cobalt salt to iron ions in the iron salt is preferably 1:(1.9-2.1), more preferably 1:2. By controlling the molar ratio of cobalt ions to iron ions within the above range, this invention can further improve the removal effect of cobalt ferrite.

[0035] In this invention, the preferred mass-to-volume ratio of the cobalt salt to water is (1.4–1.5) g:60 mL, more preferably 1.455 g:60 mL. By controlling the mass-to-volume ratio of the cobalt salt to water within the above range, this invention ensures complete dissolution of the raw materials.

[0036] In this invention, the mixing temperature of the cobalt salt, iron salt, and water is preferably room temperature; the mixing time is preferably 0.5–1.5 h, more preferably 1 h; and the mixing is preferably carried out under stirring conditions. This invention does not impose any particular limitation on the stirring method and rate; stirring techniques well-known to those skilled in the art can be used. By controlling the mixing time within the above range, this invention ensures that the raw materials are fully dissolved.

[0037] After obtaining the mixed solution, the present invention mixes the mixed solution with an alkaline solution and carries out a hydrothermal reaction to obtain cobalt ferrite.

[0038] In this invention, the alkaline solution is preferably a sodium hydroxide solution.

[0039] In this invention, the pH value of the mixed solution after mixing with the alkali solution is preferably 11-12, more preferably 12. This invention does not impose specific limitations on the concentration and amount of the alkali solution, as long as the pH value of the mixed solution after mixing with the alkali solution is within the above-mentioned range.

[0040] In this invention, the mixing temperature of the mixed solution and the alkaline solution is preferably 60–80°C, more preferably 70°C; the mixing time is preferably 0.5–1.5 h, more preferably 1 h; and the mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring method and rate; stirring techniques well known to those skilled in the art can be used.

[0041] In this invention, the temperature of the hydrothermal reaction is 155–165°C. As one embodiment, the temperature of the hydrothermal reaction can specifically be 155°C, 156°C, 157°C, 158°C, 159°C, 160°C, 161°C, 162°C, 163°C, 164°C, or 165°C.

[0042] In this invention, the hydrothermal reaction time is preferably 11-13 hours. As one embodiment, the hydrothermal reaction time can specifically be 11 hours, 11.5 hours, 12 hours, 12.5 hours, or 13 hours. By controlling the temperature and time of the hydrothermal reaction within the above range, this invention ensures that the obtained cobalt ferrite also contains iron(III) oxide. The interaction between these two elements results in the prepared cobalt ferrite exhibiting a faster removal rate when used for pollutant removal in water, enabling pollutant degradation to be completed in a shorter time.

[0043] After the hydrothermal reaction is completed, the product of the hydrothermal reaction is preferably washed with ultrapure water by centrifugation and then dried to obtain cobalt ferrite.

[0044] In this invention, the rotation speed of the ultrapure water centrifugation cleaning is preferably 9000-11000 r / min, more preferably 10000 r / min. This invention does not impose any special limitations on the amount of ultrapure water used or the number of cleaning cycles; any technical solutions well-known to those skilled in the art can be used to remove unreacted raw materials and other impurities.

[0045] In this invention, the drying temperature is preferably 50–70°C, more preferably 60°C. This invention does not have a specific limitation on the drying time; drying until the moisture is fully removed and constant weight is achieved is sufficient.

[0046] This invention prepares cobalt ferrite from cobalt and iron salts via a hydrothermal reaction. By controlling the temperature of the hydrothermal reaction, the resulting cobalt ferrite also contains iron(III) oxide (Fe3O4). The interaction between these two elements results in a faster removal rate of pollutants in water, enabling pollutant degradation in a shorter time. The cobalt ferrite prepared by this invention exhibits excellent stability and electromagnetic properties. The interaction between iron and cobalt reduces the leaching of divalent cobalt ions. Cobalt ferrite has good settling properties, allowing for rapid separation from water after use. Its magnetic properties facilitate recycling. The operation is simple and requires no pH adjustment of the water to be treated.

[0047] The present invention also provides cobalt ferrite prepared by the preparation method described in the above technical solution.

[0048] The cobalt ferrite prepared by this invention contains two phases: cobalt ferrite and iron tetroxide. When used to remove pollutants from water, it has an excellent removal effect in a short time.

[0049] The present invention also provides the application of cobalt ferrite as described above in the removal of pharmaceuticals and personal care products from water.

[0050] The present invention preferably involves mixing the water to be treated with cobalt ferrite and an oxidant for degradation to obtain purified water.

[0051] The present invention does not impose any special restrictions on the source of the water to be treated or the content of drugs and personal care products in the water; the water to be treated can be selected according to actual needs.

[0052] This invention does not impose any specific limitations on the pH value of the water to be treated; it can be selected according to actual needs. This invention eliminates the need to adjust the pH value of the water, making the treatment process simpler.

[0053] In this invention, the preferred mass ratio of cobalt ferrite to the volume of the water to be treated is (0.1–0.5) g:1 L. As one embodiment, the specific mass ratio of cobalt ferrite to the volume of the water to be treated can be 0.1 g:1 L, 0.2 g:1 L, 0.3 g:1 L, 0.4 g:1 L, or 0.5 g:1 L.

[0054] In this invention, the oxidant is preferably persulfate.

[0055] In this invention, after the water to be treated is mixed with cobalt ferrite and the oxidant, the concentration of the oxidant is preferably 0.1–0.3 mmol / L. As one embodiment, the concentration of the oxidant after mixing the water to be treated with cobalt ferrite and the oxidant can specifically be 0.1 mmol / L, 0.2 mmol / L, or 0.3 mmol / L. By controlling the mass of cobalt ferrite and the concentration of the oxidant within the above ranges, this invention can further improve the removal effect.

[0056] In this invention, the preferred method for mixing the water to be treated with cobalt ferrite and the oxidant is to mix the water to be treated and the oxidant evenly, and then add cobalt ferrite.

[0057] In this invention, the degradation temperature is preferably room temperature; the degradation is preferably carried out under stirring conditions. This invention does not impose any particular limitations on the stirring method and rate; stirring techniques well-known to those skilled in the art can be used.

[0058] The mechanism by which cobalt ferrite-activated oxidant degrades pollutants in water in this invention is as follows: Figure 1 As shown, specifically:

[0059] Use ≡Co 2+ and ≡Fe 2+ As an electron donor, it reduces permonosulfate (PMS) to produce sulfate (Equation 1-2), ≡Co 3+ and ≡Fe 3+ Can react with HSO5 - The reaction forms SO5 ·- And complete the electron valence cycle (Equation 3-4), ≡Co 2+ It is considered the main catalytic center for CoFe2O4-activated PMS, and ≡Co 2+ Regeneration is also particularly important, in addition to ≡Co 3+ Beyond conversion, regeneration ≡ Co 2+ Another important mechanism is the redox reaction between cobalt and iron, Co 3+ / Co 2+ and Fe 3+ / Fe 2+ The standard reduction potentials are 1.81V and 0.77V, respectively (Equation 5). In summary, cobalt ions and iron ions can be recycled in the system, achieving the purpose of recycling.

[0060] ≡Co 2+ +HSO5 - →≡Co 3+ +SO4 2-+·OH Formula 1,

[0061] ≡Fe 2+ +HSO5 - →≡Fe 3+ +SO4 2- +·OH (Formula 2)

[0062] ≡Co 3+ +HSO5 - →≡Co 2+ +SO5 ·- +H + Formula 3,

[0063] ≡Fe 3+ +HSO5 - →≡Fe 2+ +SO5 ·- +H + Equation 4,

[0064] ≡Co 3+ +≡Fe 2+ →≡Co 2+ +≡Fe 3+ Formula 5.

[0065] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0066] Example 1

[0067] A method for preparing cobalt ferrite: (1) 1.455g Co(NO3)2·6H2O and 4.04g Fe(NO3)3·9H2O are added to 60mL of deionized water and stirred at room temperature for 1h to obtain a mixed solution;

[0068] (2) The pH of the mixed solution was adjusted to 12 with NaOH solution. After stirring at 70℃ for 1 h, it was hydrothermally reacted at 160℃ for 12 h. After the reaction was completed, the solution was washed with ultrapure water by centrifugation at 10000 r / min and dried at 60℃ to obtain cobalt ferrite.

[0069] Comparative Example 1

[0070] The temperature of the hydrothermal reaction in Example 1 was replaced with 180°C, and all other parameters were the same as in Example 1.

[0071] The cobalt ferrite prepared in Example 1 was observed using a scanning electron microscope (SEM), and the SEM images obtained at different magnifications are shown below. Figures 2-3 As shown, where Figure 2 Scaled up to 500nm, Figure 3 Magnified to 1 μm. The XRD pattern of cobalt ferrite prepared in Example 1 is shown below. Figure 4 As shown. From Figures 2-4 As can be seen from the image, the cobalt ferrite prepared in Example 1 is spherical. In addition, a small number of plate-like structures were also found during the scanning process. Figure 4 The X-ray diffraction pattern, combined with analysis, indicates that it is iron(III) oxide (Fe3O4). Since the characteristic peaks of CoFe2O4 (PDF#79-1744) and Fe3O4 (PDF#88-0866) are very close and indistinguishable, and no other characteristic peaks were found in the crystal structure, the cobalt ferrite prepared in Example 1 should contain only two phases.

[0072] Application Example 1

[0073] The water containing bisphenol A (bisphenol A concentration of 10 mg / L, pH of the water to be treated is 6.32) was mixed evenly with persulfate, and the concentration of persulfate after mixing was 0.2 mmol / L (0.2 mM). Then, cobalt ferrite prepared in Example 1 was added and mixed evenly. The mass ratio of cobalt ferrite to the volume of the water to be treated was 0.3 g: 1 L (0.3 g / L). The mixture was stirred at room temperature for 15 min, and the removal rate of bisphenol A at different reaction times was tested.

[0074] Application Example 2

[0075] Replace the concentration of persulfate in Application Example 1 with 0.1 mmol / L (0.1 mM), and keep all other parameters the same as in Application Example 1.

[0076] Application Example 3

[0077] Replace the concentration of persulfate in Application Example 1 with 0.3 mmol / L (0.3 mM), and keep all other parameters the same as in Application Example 1.

[0078] Application Example 4

[0079] Replace the mass ratio of cobalt ferrite to the volume ratio of the water to be treated in Application Example 1 with 0.1 g: 1 L (0.1 g / L), and keep all other parameters the same as in Application Example 1.

[0080] Application Example 5

[0081] Replace the mass ratio of cobalt ferrite to the volume ratio of the water to be treated in Application Example 1 with 0.2 g: 1 L (0.2 g / L), and keep all other parameters the same as in Application Example 1.

[0082] Application Example 6

[0083] Replace the mass ratio of cobalt ferrite to the volume ratio of the water to be treated in Application Example 1 with 0.4 g: 1 L (0.4 g / L), and keep all other parameters the same as in Application Example 1.

[0084] Comparative Application Example 1

[0085] Replace the concentration of persulfate in Application Example 1 with 0 mmol / L (0 mM), i.e. omit the oxidant, and keep all other parameters the same as in Application Example 1.

[0086] Comparative Application Example 2

[0087] Replace the mass ratio of cobalt ferrite to the volume ratio of the water to be treated in Application Example 1 with 0 g: 1 L (0 g / L), i.e. omit cobalt ferrite, and keep all other parameters the same as in Application Example 1.

[0088] Comparative Application Example 3

[0089] The cobalt ferrite prepared in Example 1 of Application Example 1 was replaced with the cobalt ferrite prepared in Comparative Example 1, and all other parameters were the same as in Application Example 1.

[0090] The removal rates of bisphenol A in Application Examples 1-3 and Comparative Application Example 1 are as follows: Figure 5 As shown. From Figure 5 It can be seen that when the cobalt ferrite dosage is 0.3 g / L, the optimal dosage of persulfate is 0.2 mmol / L.

[0091] The removal rates of bisphenol A in Application Examples 1, 4-6 and Comparative Application Example 2 are as follows: Figure 6 As shown. From Figure 6 It can be seen that when the persulfate concentration is 0.2 mmol / L, the optimal dosage of cobalt ferrite is 0.3 g / L.

[0092] The removal rates of bisphenol A in Application Example 1 and Comparative Application Example 3 are as follows: Figure 7 As shown. From Figure 7 As can be seen, compared with Comparative Application Example 3, the cobalt ferrite prepared by the present invention can complete the degradation and removal of bisphenol A in a shorter time.

[0093] In summary, this invention controls the temperature of the hydrothermal reaction, enabling the prepared cobalt ferrite to have a shorter removal time when used to remove pollutants from water.

[0094] 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. An application of cobalt ferrite in the removal of bisphenol A from water, comprising mixing the water to be treated with cobalt ferrite and an oxidant for degradation to obtain purified water; wherein the mass ratio of cobalt ferrite to the volume of the water to be treated is 0.3 g: 1 L; the concentration of the oxidant after mixing the water to be treated with cobalt ferrite and the oxidant is 0.2 mmol / L; the cobalt ferrite contains iron(III) oxide; the concentration of bisphenol A in the water to be treated is 10 mg / L; the pH value of the water to be treated is 6.32; and the oxidant is persulfate. The method for preparing cobalt ferrite includes the following steps: (1) Mix cobalt salt, iron salt and water to obtain a mixed solution; (2) The mixed solution obtained in step (1) is mixed with an alkaline solution and subjected to a hydrothermal reaction to obtain cobalt ferrite; In step (1), the cobalt salt is Co(NO3)2·6H2O; the molar ratio of cobalt ions in the cobalt salt to iron ions in the iron salt is 1:2; the mass ratio of cobalt salt to water in step (1) is 1.455g:60mL; the pH value of the mixed solution after mixing with the alkali solution in step (2) is 12; the temperature of the hydrothermal reaction in step (2) is 160℃, and the time of the hydrothermal reaction is 12h.

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