Cobalt ferrite and preparation method and application thereof

Abstract

The invention provides cobalt ferrite as well as a preparation method and application thereof, and belongs to the technical field of water treatment. The preparation method provided by the invention comprises the following steps: (1) mixing cobalt salt, ferric salt and water to obtain a mixed solution; (2) mixing the mixed solution obtained in the step (1) with alkali liquor, and carrying out hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155 to 165 DEG C. The cobalt salt and the iron salt are used as raw materials, the cobalt ferrite is prepared through the hydrothermal reaction, the temperature of the hydrothermal reaction is controlled, the obtained cobalt ferrite further contains ferroferric oxide, and the cobalt ferrite and the ferroferric oxide interact with each other, so that the prepared cobalt ferrite has a higher removal rate when being used for removing pollutants in a water body, and degradation of the pollutants can be completed within a shorter time. The result of the embodiment shows that when the prepared cobalt ferrite is used for removing bisphenol A in a water body, the removal rate of the cobalt ferrite reaches nearly 100% within 5 minutes.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to cobalt ferrite and a preparation method and application thereof. Background Art

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

[0003] The methods currently used to remove PPCPs from water bodies mainly include biological, physical and chemical methods. The removal effect of traditional biological treatment processes on PPCPs is limited, and the treatment time is long. The wastewater is prone to deterioration such as discoloration and taste change. It is usually necessary to combine it with other methods to remove PPCPs from various types of wastewater. Physical methods for treating PPCPs cannot change the chemical structure of pollutants, and there is still a risk of migration and transformation after removal. Advanced oxidation technology in chemical methods is considered to be a very promising way to degrade pollutants. This method requires suitable external conditions to activate the oxidant. Although there are methods in the prior art that use cobalt ferrite to activate oxidants to remove pollutants in water, the cobalt ferrite in the prior art has a slow removal rate and a long removal time when used to remove pollutants in water. Summary of the Invention

[0004] The present invention aims to provide a cobalt ferrite and its preparation method and application. The cobalt ferrite prepared by the preparation method provided by the present invention has a fast removal rate and a short removal time when used to remove pollutants in water.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

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

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

[0008] (2) mixing the mixed solution obtained in step (1) with alkaline solution and performing a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165°C.

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

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

[0011] Preferably, the pH value of the mixed solution after mixing with the alkali solution in step (2) is 11-12.

[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 use of the cobalt ferrite described in the above technical solution in removing medicines or personal care products from water.

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

[0016] Preferably, the mass ratio of the cobalt ferrite to the volume 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 an oxidant, the concentration of the oxidant is 0.1 to 0.3 mmol / L.

[0018] The present invention provides a method for preparing cobalt ferrite, comprising the following steps: (1) mixing a cobalt salt, an iron salt, and water to obtain a mixed solution; (2) mixing the mixed solution obtained in step (1) with an alkaline solution and performing a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165°C. The present invention uses cobalt salt and iron salt as raw materials to prepare cobalt ferrite through a hydrothermal reaction. The temperature of the hydrothermal reaction is controlled so that the obtained cobalt ferrite also contains ferrosoferric oxide. The interaction between the two allows the prepared cobalt ferrite to have a faster removal rate when used to remove pollutants from water bodies, and the pollutants can be degraded in a shorter time. The results of the examples show that when the cobalt ferrite prepared by the present invention is used to remove bisphenol A from water bodies, its removal rate reaches nearly 100% in 5 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The diagram shows the mechanism of using cobalt ferrite to degrade PPCPs in water.

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

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

[0022] Figure 4 This is the XRD pattern of the cobalt ferrite prepared in Example 1;

[0023] Figure 5is the removal rate of bisphenol A in Application Examples 1 to 3 and Comparative Application Example 1;

[0024] Figure 6 is the removal rate of bisphenol A in Application Examples 1, 4 to 6 and Comparative Application Example 2;

[0025] Figure 7 is the removal rate of bisphenol A in Application Example 1 and Comparative Application Example 3. DETAILED DESCRIPTION

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

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

[0028] (2) mixing the mixed solution obtained in step (1) with alkaline solution and performing a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165°C.

[0029] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0030] The invention mixes cobalt salt, iron salt and water to obtain a mixed solution.

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

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

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

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

[0035] In the present invention, the mass ratio of the cobalt salt to the volume ratio of water is preferably (1.4-1.5) g:60 mL, more preferably 1.455 g:60 mL. The present invention controls the mass ratio of the cobalt salt to the volume ratio of water within the above range to fully dissolve the raw materials.

[0036] In the present invention, the cobalt salt, iron salt, and water are preferably mixed at room temperature; the mixing time is preferably 0.5 to 1.5 hours, more preferably 1 hour; and the mixing is preferably performed under stirring. The present invention does not specifically limit the stirring method or rate; stirring techniques familiar to those skilled in the art can be employed. Controlling the mixing time within the aforementioned range allows for sufficient dissolution of the raw materials.

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

[0038] In the present invention, the alkali solution is preferably a sodium hydroxide solution.

[0039] In the present invention, the pH value of the mixed solution after mixing with the alkali solution is preferably 11-12, more preferably 12. The present invention has no particular limitation 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 range.

[0040] In the present invention, the temperature for mixing the mixed solution and the alkali solution is preferably 60-80°C, more preferably 70°C; the mixing time is preferably 0.5-1.5 hours, more preferably 1 hour; and the mixing is preferably performed under stirring conditions. The present invention does not specifically limit the stirring method and rate; stirring techniques well known to those skilled in the art can be used.

[0041] In the present invention, the temperature of the hydrothermal reaction is 155-165° C. As an embodiment, the temperature of the hydrothermal reaction can be specifically 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 the present invention, the hydrothermal reaction time is preferably 11 to 13 hours. As an embodiment, the hydrothermal reaction time can specifically be 11 hours, 11.5 hours, 12 hours, 12.5 hours, or 13 hours. The present invention controls the temperature and time of the hydrothermal reaction within the above ranges, so that the obtained cobalt ferrite also contains ferrosoferric oxide. The interaction between the two allows the prepared cobalt ferrite to have a faster removal rate when used to remove pollutants from water bodies, and the degradation of pollutants can be completed in a shorter time.

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

[0044] In the present invention, the rotation speed of the ultrapure water centrifugal washing is preferably 9000-11000 r / min, more preferably 10000 r / min. The present invention has no particular limitation on the amount of ultrapure water used and the number of washing times. Impurities such as unreacted raw materials can be removed using technical solutions well known to those skilled in the art.

[0045] In the present invention, the drying temperature is preferably 50-70° C., more preferably 60° C. The present invention has no particular limitation on the drying time, as long as the moisture is fully removed and the product is dried to a constant weight.

[0046] The present invention uses cobalt salt and iron salt as raw materials to produce cobalt ferrite through a hydrothermal reaction. The temperature of the hydrothermal reaction is controlled so that the resulting cobalt ferrite also contains ferrosoferric oxide. The interaction between the two allows the prepared cobalt ferrite to remove pollutants from water at a faster removal rate, effectively degrading pollutants in a shorter time. The cobalt ferrite prepared by the present invention has excellent stability and electromagnetic properties. The interaction between iron and cobalt reduces the leaching of divalent cobalt ions. The cobalt ferrite has good sedimentation properties and can be separated from water in a short time after use. Its magnetic properties make it easier to recover. The operation process is simple during use, and there is no need to adjust the pH value 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 the invention contains two phases of cobalt ferrite and ferrosoferric oxide, and has an excellent removal effect in a short time when used for removing pollutants in water.

[0049] The present invention also provides the use of the cobalt ferrite described in the above technical solution in removing medicines and personal care products from water bodies.

[0050] In the present invention, the water body to be treated is preferably mixed with cobalt ferrite and an oxidant to perform degradation to obtain purified water.

[0051] The present invention has no special limitation on the source of the water to be treated and the content of medicines and personal care products in the water to be treated. The water to be treated can be selected according to actual needs.

[0052] The present invention has no special limitation on the pH value of the water to be treated, and can be selected according to actual needs. The present invention does not require adjusting the pH value of the water to be treated, and the treatment process is simpler.

[0053] In the present invention, the mass ratio of the cobalt ferrite to the volume of the water to be treated is preferably (0.1-0.5) g:1 L. As an embodiment, the mass ratio of the cobalt ferrite to the volume of the water to be treated can be specifically 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 the present invention, the oxidizing agent is preferably peroxymonosulfate.

[0055] In the present invention, after the water to be treated is mixed with cobalt ferrite and an oxidant, the concentration of the oxidant is preferably 0.1 to 0.3 mmol / L. In one embodiment, after the water to be treated is mixed with cobalt ferrite and an oxidant, the concentration of the oxidant can be specifically 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, the present invention can further improve the removal effect.

[0056] In the present invention, the mixing of the water to be treated, the cobalt ferrite and the oxidant is preferably carried out by uniformly mixing the water to be treated and the oxidant, and then adding the cobalt ferrite.

[0057] In the present invention, the degradation temperature is preferably room temperature; the degradation is preferably carried out under stirring conditions. The present invention has no particular limitation on the stirring method and rate, and any stirring technical solution well known to those skilled in the art can be used.

[0058] The mechanism of the cobalt ferrite activating oxidant to degrade pollutants in water is as follows: Figure 1 As shown, specifically:

[0059] Using ≡Co 2+ and ≡Fe 2+ As an electron donor to reduce peroxymonosulfate (PMS) to produce sulfate (Formula 1-2), ≡Co 3+ and ≡Fe 3+ Can react with HSO5 - Reaction to form SO5 ·- And complete the electronic valence cycle (Formula 3-4), ≡Co 2+ is considered to be the main catalytic center of CoFe2O4 activated PMS, and ≡Co 2+ The regeneration of 3+ In addition to conversion, regeneration ≡Co 2+ Another important way is the redox reaction between cobalt and iron. 3+ / Co 2+ and Fe 3+ / Fe 2+ The standard reduction potentials of are 1.81 V and 0.77 V respectively (Formula 5). In summary, cobalt ions and iron ions can be recycled in the system to achieve 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 + Formula 4,

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

[0065] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0066] Example 1

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

[0068] (2) The pH value of the mixed solution was adjusted to 12 with NaOH solution, and the mixture was stirred at 70°C for 1 hour and then hydrothermally reacted at 160°C for 12 hours. After the reaction was completed, the obtained solution was centrifuged and washed with ultrapure water at a speed of 10,000 r / min and dried at 60°C to obtain cobalt ferrite.

[0069] Comparative Example 1

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

[0071] The cobalt ferrite prepared in Example 1 was observed using a scanning electron microscope, and the SEM images obtained at different magnifications were as follows: Figures 2-3 As shown, Figure 2 Zoom in to 500nm, Figure 3 Zoom in to 1 μm. The XRD pattern of cobalt ferrite prepared in Example 1 is as follows Figure 4 As shown. Figures 2-4 It can be seen from the figure that the cobalt ferrite prepared in Example 1 is spherical. In addition, a small amount of flake structures were also found during the scanning process, which is consistent with the Figure 4 The X-ray diffraction spectrum of the cobalt ferrite prepared in Example 1 should be ferrosoferric oxide. Since the characteristic peaks of CoFe2O4 (PDF#79-1744) and Fe3O4 (PDF#88-0866) are very close and cannot be distinguished, and no other characteristic peaks are found in the crystal structure, the cobalt ferrite prepared in Example 1 should only contain two phases.

[0072] Application Example 1

[0073] The water to be treated containing bisphenol A (the concentration of bisphenol A is 10 mg / L and the pH value of the water to be treated is 6.32) was mixed evenly with peroxymonosulfate, and the concentration of peroxymonosulfate after mixing was 0.2 mmol / L (0.2 mM). The cobalt ferrite prepared in Example 1 was then added and mixed evenly, and 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 minutes, and the removal rate of bisphenol A was tested at different reaction times.

[0074] Application Example 2

[0075] The concentration of peroxymonosulfate in Application Example 1 was replaced with 0.1 mmol / L (0.1 mM), and the other parameters were the same as those in Application Example 1.

[0076] Application Example 3

[0077] The concentration of peroxymonosulfate in Application Example 1 was replaced with 0.3 mmol / L (0.3 mM), and the other parameters were the same as those in Application Example 1.

[0078] Application Example 4

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

[0080] Application Example 5

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

[0082] Application Example 6

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

[0084] Comparative Application Example 1

[0085] The concentration of peroxymonosulfate in Application Example 1 was replaced with 0 mmol / L (0 mM), that is, the oxidant was omitted, and the other parameters were the same as those in Application Example 1.

[0086] Comparative Application Example 2

[0087] The mass ratio of cobalt ferrite to the volume of the water to be treated in Application Example 1 is replaced with 0 g:1 L (0 g / L), that is, cobalt ferrite is omitted, and other parameters are the same as those in Application Example 1.

[0088] Comparative Application Example 3

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

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

[0091] The removal rates of bisphenol A in application examples 1, 4 to 6 and comparative application example 2 are as follows: Figure 6 As shown. Figure 6 It can be seen that when the concentration of peroxymonosulfate is 0.2mmol / L, the optimal dosage of cobalt ferrite is 0.3g / L.

[0092] The removal rates of bisphenol A in Application Example 1 and Comparative Application Example 3 are as follows: Figure 7 As shown. Figure 7 It can be seen that 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, the present invention controls the temperature of the hydrothermal reaction so that the prepared cobalt ferrite has a shorter removal time when used to remove pollutants in water.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing cobalt ferrite, comprising the following steps: (1) mixing a cobalt salt, an iron salt and water to obtain a mixed solution; (2) mixing the mixed solution obtained in step (1) with alkaline solution and performing a hydrothermal reaction to obtain cobalt ferrite; the temperature of the hydrothermal reaction is 155-165°C.

2. The preparation method according to claim 1, characterized in that In the step (1), the molar ratio of the cobalt ions in the cobalt salt to the iron ions in the iron salt is 1:(1.9-2.1).

3. The preparation method according to claim 1, characterized in that The mass ratio of the cobalt salt to the volume ratio of water in the step (1) is (1.4-1.5) g:60 mL.

4. The preparation method according to claim 1, characterized in that The pH value of the mixed solution after mixing with the alkali solution in step (2) is 11-12.

5. The preparation method according to claim 1, characterized in that The hydrothermal reaction time in step (2) is 11 to 13 hours.

6. Cobalt ferrite prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the cobalt ferrite according to claim 6 in removing medicines or personal care products from water.

8. The use according to claim 7, characterized in that The water to be treated is mixed with cobalt ferrite and an oxidant to be degraded to obtain purified water.

9. The use according to claim 8, characterized in that The mass ratio of the cobalt ferrite to the volume of the water to be treated is (0.1-0.5) g:1L.

10. The use according to claim 8, characterized in that After the water to be treated is mixed with cobalt ferrite and an oxidant, the concentration of the oxidant is 0.1 to 0.3 mmol / L.

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