Method for low-temperature one-step synthesis of strong magnetic hydrophobic fe3o4 nanoparticles, fe3o4 nanoparticles and application

Abstract

The application relates to a method for one-step synthesis of strong magnetic hydrophobic Fe3O4 nanoparticles at low temperature and the Fe3O4 nanoparticles and application, and belongs to the technical field of nano material preparation. The method comprises the following steps: adding a ferrous sulfate solution into a mixed solution of sodium hydroxide and sodium nitrate, heating and stirring to react, adding oleic acid in the reaction process, and obtaining black Fe3O4 crystals after the reaction is completed. The saturation magnetization of the obtained strong magnetic hydrophobic Fe3O4 nanoparticles can reach 85.69 emu / g at most, and the water contact angle can reach 148.95 DEG. The one-step synthesis reaction only needs to use oleic acid as a regulator, avoids an extreme high-temperature and high-pressure environment, does not need to use a toxic chemical solvent, the condition is mild, the process is simple, the operation condition is easy to control, and the method has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial preparation, and particularly relates to a method for synthesizing strong magnetic hydrophobic Fe3O4 nanoparticles at low temperature in one step, Fe3O4 nanoparticles and application thereof. BACKGROUND

[0002] In recent years, due to the frequent discharge of oily sewage and oil spill accidents, the problem of oil-water pollution is becoming increasingly serious, which not only causes damage to the ecological environment, but also seriously threatens human health. Therefore, it is of great significance to develop efficient oil-water separation technology. The existence form of oil in water mainly includes suspended oil (≥100 μm), dispersed oil (10-100 μm) and emulsified oil (0.1-10 μm). Among them, emulsified oil droplets have small particle size and strong stability, and it is difficult to realize efficient oil-water separation by conventional methods such as air flotation and centrifugation, which is a big problem in the field of oil-water separation. At present, the methods for treating emulsified oil mainly include membrane separation method and flocculation sedimentation method, but these methods still have some drawbacks, such as membrane separation method is easy to be polluted and the effect is not lasting, flocculation sedimentation method is easy to form floating flocs and has low separation efficiency, which limits their development and application. The magnetic separation process has attracted widespread attention in the field of oil-water separation due to its convenience and efficiency. Fe3O4 magnetic nanoparticles have simple preparation and strong surface modification, and have broad application prospects in oily wastewater treatment.

[0003] At present, the surface modification of Fe3O4 magnetic nanoparticles mainly includes two-step method and one-step method. The two-step method (for example, CN103833942A, CN103920471A, CN104403041A, CN104531119A) needs to synthesize Fe3O4 magnetic nanoparticles first, and then use hydrophobic or amphiphilic substances to modify the surface, which is complex and tedious, and the reaction period is long, so it is not suitable for large-scale production. The one-step method (for example, CN103212352A) usually needs high temperature and high pressure environment, involves toxic chemical solvents, has harsh reaction conditions, and is easy to cause secondary pollution; in addition, the coprecipitation method (for example, CN102580783A, CN105061663A) can also synthesize oleic acid modified Fe3O4 magnetic nanoparticles in one step, but the product obtained has poor crystallinity and weak magnetism, which is not conducive to the recycling of Fe3O4 magnetic nanoparticles. SUMMARY

[0004] In view of the deficiencies of the prior art, the application provides a method for one-step synthesis of strong magnetic hydrophobic Fe3O4 nanoparticles at low temperature, and the Fe3O4 nanoparticles and application thereof. Under the condition of low temperature, the growth process of magnetite is controlled by using natural hydrophobic organic matter, i.e., oleic acid, as a regulator, and the surface of the magnetite is modified to be hydrophobic; the synthesized Fe3O4 nanoparticles have strong magnetism and are easy to recycle; meanwhile, the extreme high-temperature and high-pressure environment is avoided, the regulator is non-toxic and non-polluting, the condition is mild, the process is simple, the operation condition is easy to control, and the method has wide application prospect.

[0005] In order to realize the above technical purposes, the application adopts the following technical scheme:

[0006] A method for one-step synthesis of strong magnetic hydrophobic Fe3O4 nanoparticles at low temperature, comprising the following steps: adding a ferrous salt solution into a mixed solution of sodium hydroxide and sodium nitrate, heating to 40-80 DEG C and stirring to react, adding oleic acid during the reaction, and obtaining black Fe3O4 crystals after the reaction, and then centrifuging, washing and freeze-drying to obtain strong magnetic hydrophobic Fe3O4 nanoparticles; wherein the initial pH of the reaction is 8-13, the initial Fe 2+ concentration is 0.11-0.25 mol / L, and the initial NO3 - concentration is 0.18-0.55 mol / L.

[0007] Preferably, the adding time of the oleic acid is 0-3 h, and the adding amount is 10-300 muL.

[0008] Preferably, the adding time of the oleic acid is 1-2 h, and the adding amount is 100 muL.

[0009] Preferably, the ferrous salt is any one of ferrous sulfate or ferrous chloride.

[0010] Preferably, the initial NO3 - concentration is 0.18 mol / L.

[0011] Preferably, the initial pH of the reaction is 9-11, and more preferably 11.

[0012] Preferably, the initial Fe 2+ concentration is 0.18 mol / L.

[0013] Preferably, the stirring rate is 500-1000 rpm, and more preferably 500-700 rpm.

[0014] Preferably, the reaction time is 3-8 h, and more preferably 5 h.

[0015] The strong magnetic hydrophobic Fe3O4 magnetic nanoparticles prepared by the method.

[0016] The application of the strong magnetic hydrophobic Fe3O4 magnetic nanoparticles as an adsorbent in oil-containing wastewater.

[0017] Principle of the present application:

[0018] The reaction equation of the present application is: 3Fe 2+ +6OH-+NO3 - →Fe3O4+NO2 - +3H2O, under alkaline conditions, Fe 2+ first combines with OH - to form Fe(OH)2, and NO3 - can oxidize part of Fe 2+ to Fe 3+ , and Fe3O4 is synthesized. By adding oleic acid during the growth of Fe3O4 magnetic nanoparticles, the -COOH of the oleic acid preferentially combines with the (001) and (111) crystal faces of the Fe3O4 crystal, directional adjustment of the growth of the Fe3O4 crystal is realized, and the surface of the Fe3O4 crystal is modified, the magnetism and hydrophobicity of the Fe3O4 crystal are improved.

[0019] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0020] The magnetism of the Fe3O4 nanoparticles synthesized by the one-step method of the present application is obviously enhanced, and the saturation magnetization is as high as 85.69emu / g, while the saturation magnetization of the magnetic nanoparticles synthesized without adding oleic acid is 62.27emu / g, which is increased by 37.6%. The magnetite synthesized by adding oleic acid has a hydrophobic surface, and the water contact angle is 148.95°, while the water contact angle of the magnetic nanoparticles synthesized without adding oleic acid is 30.84°, and the surface is hydrophilic.

[0021] The present application realizes the surface modification of Fe3O4 magnetic nanoparticles by using oleic acid as a control agent under low temperature conditions through a one-step method, and also improves the magnetism of the Fe3O4 nanoparticles, which is a very potential emulsified oil adsorption material. The method of the present application is simple, the conditions are mild, the operability is strong, the oleic acid used is cheap and easy to obtain, and the application prospect is broad. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The XRD spectrum of the Fe3O4 magnetic nanoparticles obtained in Example 1 of the present application at different addition times.

[0023] Figure 2 The M-H curve of the Fe3O4 magnetic nanoparticles obtained in Example 1 of the present application at different addition times.

[0024] Figure 3 The water contact angle of Fe3O4 magnetic nanoparticles obtained in Example 1 of the present application at different dosing times is shown in the following figure.

[0025] Figure 4 The SEM image of Fe3O4 magnetic nanoparticles obtained in Example 1 of the present application at different dosing times is shown in the following figure.

[0026] Figure 5 The M-H curve of Fe3O4 magnetic nanoparticles obtained in Example 2 of the present application at different dosing amounts is shown in the following figure.

[0027] Figure 6 The water contact angle of Fe3O4 magnetic nanoparticles obtained in Example 2 of the present application at different dosing amounts is shown in the following figure.

[0028] Figure 7 The saturation magnetization of Fe3O4 magnetic nanoparticles obtained in Example 3 of the present application at different NaNO3 concentrations is shown in the following figure.

[0029] Figure 8 The water contact angle of Fe3O4 magnetic nanoparticles obtained in Example 3 of the present application at different NaNO3 concentrations is shown in the following figure.

[0030] Figure 9 The XRD spectrum of Fe3O4 magnetic nanoparticles obtained in Example 4 of the present application at different initial pH conditions is shown in the following figure.

[0031] Figure 10 The saturation magnetization of Fe3O4 magnetic nanoparticles obtained in Example 4 of the present application at different initial pH conditions is shown in the following figure.

[0032] Figure 11 The water contact angle of Fe3O4 magnetic nanoparticles obtained in Example 4 of the present application at different initial pH conditions is shown in the following figure.

[0033] Figure 12 The saturation magnetization of Fe3O4 magnetic nanoparticles obtained in Example 5 of the present application at different initial Fe 2+ concentrations is shown in the following figure.

[0034] Figure 13 The water contact angle of Fe3O4 magnetic nanoparticles obtained in Example 5 of the present application at different initial Fe 2+ concentrations is shown in the following figure.

[0035] Figure 14 The saturation magnetization of Fe3O4 magnetic nanoparticles obtained in Example 6 of the present application at different temperatures is shown in the following figure.

[0036] Figure 15 Figure 6 is a comparison chart of the water contact angles of Fe304 magnetic nanoparticles obtained at different temperatures in Example 6 of the present application.

[0037] Figure 16 Figure 7 is a comparison chart of the saturation magnetization of Fe304 magnetic nanoparticles obtained at different stirring rates in Example 7 of the present application.

[0038] Figure 17 Figure 8 is a comparison chart of the water contact angles of Fe304 magnetic nanoparticles obtained at different stirring rates in Example 7 of the present application.

[0039] Figure 18 Figure 9 is a comparison chart of the saturation magnetization of Fe304 magnetic nanoparticles obtained at different reaction times in Example 8 of the present application.

[0040] Figure 19 Figure 10 is a comparison chart of the water contact angles of Fe304 magnetic nanoparticles obtained at different reaction times in Example 8 of the present application. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the examples.

[0042] It should be understood that the specific examples described herein merely exemplify the present application and do not limit the same.

[0043] In the examples, unless otherwise specified, the means used are conventional means in the art.

[0044] The technical solutions of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all the other examples obtained by those skilled in the art without any creative effort fall within the scope of the present application.

[0045] In addition, the technical features involved in each of the embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0046] The reagents and instruments used in the examples and comparative examples of the present application are commercially available.

[0047] Example 1

[0048] Take 30 mL of 0.67 mol / L NaOH solution and 5 mL of 4 mol / L NaNO3 solution respectively and mix them in a 100 mL Erlenmeyer flask to form a bottom solution. Then add 20 mL of 0.5 mol / L FeSO4 solution to each flask and adjust the pH to 10 with dilute sulfuric acid or sodium hydroxide solution. Seal the Erlenmeyer flask with a rubber stopper and place it in a 40℃ water bath at 500 rpm. Add 100 μL of oleic acid at 0 min, 30 min, 1 h, 2 h, and 3 h after the start of the reaction. After 5 h of reaction, enrich Fe3O4 crystals with a magnet. Wash once with ethanol and then three times with deionized water. Centrifuge at 4000 rpm for 3 min, discard the supernatant, freeze-dry the precipitate, and perform VSM, contact angle, and SEM tests. The results are as follows. Figures 1-4 As shown.

[0049] from Figure 1 It can be seen that the precipitate produced by the reaction is Fe3O4 crystals. Furthermore, according to... Figure 2 VSM testing and Figure 3 The contact angle test results show that the synthesized Fe3O4 magnetic nanoparticles exhibited the strongest magnetism (76.24 emu / g) and the best hydrophobicity (138.29° water contact angle) when oleic acid was added 2 hours after the reaction began. Figure 4 It can be seen that when oleic acid is added in the 2nd hour, the morphology of Fe3O4 nanoparticles is more regular and the particle size is relatively larger.

[0050] Example 2

[0051] Take 30 mL of 0.67 mol / L NaOH solution and 5 mL of 4 mol / L NaNO3 solution respectively and mix them in a 100 mL Erlenmeyer flask to form a bottom solution. Then add 20 mL of 0.5 mol / L FeSO4 solution to each flask and adjust the pH to 10 with dilute sulfuric acid or sodium hydroxide solution. Seal the Erlenmeyer flask with a rubber stopper and place it in a 40℃ water bath at 500 rpm. At the second hour after the start of the reaction, add 0 μL, 10 μL, 50 μL, 100 μL, 200 μL, and 300 μL of oleic acid respectively. After reacting for 5 hours, enrich Fe3O4 crystals with a magnet. Wash once with ethanol and then three times with deionized water. Centrifuge at 4000 rpm for 3 min, discard the supernatant, freeze-dry the precipitate and characterize it.

[0052] from Figure 5 and Figure 6 It can be seen that when the amount of oleic acid added is 10uL, 50uL, and 100uL, the saturation magnetization Ms of the synthesized Fe3O4 nanoparticles is very close, about 77 emu / g, and the hydrophobicity is also very close, with a water contact angle of about 137°.

[0053] Example 3

[0054] Prepare 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L NaNO3 solution respectively, then take 30 mL 0.67 mol / L NaOH solution and 5 mL NaNO3 solution of corresponding concentration into 100 mL conical flask to mix into the bottom liquid, then add 20 mL 0.5 mol / L FeSO4 solution into it respectively, the concentration of NaNO3 in the mixed reaction liquid is 0.045 mol / L, 0.09 mol / L, 0.18 mol / L, 0.36 mol / L and 0.55 mol / L respectively, adjust pH to 10 with dilute sulfuric acid or sodium hydroxide solution; then seal the conical flask with rubber plug, place it in 40℃ water bath, set the rotation speed to 500 rpm, add 100 uL oleic acid at the 2nd hour after the reaction starts, after 5 h reaction, enrich Fe3O4 crystal with magnet, wash it with ethanol for 1 time first, then wash it with deionized water for 3 times, then centrifuge at 4000 rpm for 3 min, pour off the supernatant, freeze dry the precipitate and then characterize it.

[0055] From Figure 7 and Figure 8 It can be seen that when the concentration of NaNO3 in the reaction liquid is 0.18 mol / L, the synthesized Fe3O4 nanoparticles have the strongest magnetism and the best hydrophobicity, the saturation magnetization Ms is 80.38 emu / g, and the water contact angle is 143.98°.

[0056] Example 4

[0057] Take 30 mL 0.67 mol / L NaOH solution and 5 mL 2 mol / L NaNO3 solution into 100 mL conical flask to mix into the bottom liquid, then add 20 mL 0.5 mol / L FeSO4 solution into it respectively, adjust pH to 8, 9, 10, 11, 12, 13, 14 respectively with dilute sulfuric acid or sodium hydroxide solution; then seal the conical flask with rubber plug, place it in 40℃ water bath, set the rotation speed to 500 rpm, add 100 uL oleic acid at the 2nd hour after the reaction starts, after 5 h reaction, enrich Fe3O4 crystal with magnet, wash it with ethanol for 1 time first, then wash it with deionized water for 3 times, then centrifuge at 4000 rpm for 3 min, pour off the supernatant, freeze dry the precipitate and then characterize it.

[0058] From Figure 9 It can be seen that when the initial pH is in the range of 8-13, Fe3O4 crystal can be synthesized, but when the initial pH is 14, the product after reaction is FeOOH; from Figure 10 and Figure 11It can be seen that when the initial pH is 11, the saturation magnetization of the synthesized Fe3O4 crystal is the highest, reaching 80.66 emu / g, and the contact angle is also the largest, reaching 146.57°.

[0059] Example 5

[0060] respectively, and then 30 mL of 0.67 mol / L NaOH solution and 5 mL of 2 mol / L NaNO3 solution were mixed in a 100 mL conical flask to form a bottom solution, and then 20 mL of FeSO4 solution with the corresponding concentration was added, respectively. The initial Fe 2+ The concentration was 0.11 mol / L, 0.15 mol / L, 0.18 mol / L, 0.22 mol / L and 0.25 mol / L, respectively, and the pH was adjusted to 11 with dilute sulfuric acid or sodium hydroxide solution. Then the conical flask was tightly plugged with a rubber plug, and was placed in a 40℃ water bath with a rotation speed of 500 rpm. 100 uL of oleic acid was added at the 2nd hour after the reaction started, and the Fe3O4 crystal was enriched with a magnet after 5 hours of reaction. The Fe3O4 crystal was washed once with ethanol and then three times with deionized water, and then was centrifuged at 4000 rpm for 3 min. The supernatant was discarded, and the precipitate was freeze-dried for characterization.

[0061] From the above results, it can be seen that when the initial Fe Figure 12 and Figure 13 It can be seen that when the initial Fe 2+ The magnetic property and hydrophobicity of the synthesized Fe3O4 crystal are the best when the initial Fe

[0062] Example 6

[0063] This example compares the effect of reaction temperature on the performance of the synthesized magnetic nanoparticles, and the specific process is as follows:

[0064] 30 mL of 0.67 mol / L NaOH solution and 5 mL of 2 mol / L NaNO3 solution were mixed in a 100 mL conical flask to form a bottom solution, and then 20 mL of 0.5 mol / L FeSO4 solution was added, and the pH was adjusted to 11 with dilute sulfuric acid or sodium hydroxide solution. Then the conical flask was tightly plugged with a rubber plug, and was placed in a 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ water bath, respectively, with a rotation speed of 500 rpm. 100 uL of oleic acid was added at the 2nd hour after the reaction started, and the Fe3O4 crystal was enriched with a magnet after 5 hours of reaction. The Fe3O4 crystal was washed once with ethanol and then three times with deionized water, and then was centrifuged at 4000 rpm for 3 min. The supernatant was discarded, and the precipitate was freeze-dried for characterization.

[0065] By Figure 14 And Figure 15 It can be seen that when the reaction temperature is 40℃ and above, the magnetism of Fe3O4crystals has a slight upward trend, but the change is not large; but the water contact angle decreases with the increase of temperature, so the optimal temperature is selected as 40℃.

[0066] Example 7

[0067] This example compares the effect of stirring rate on the performance of the synthesized magnetic nanoparticles, and the specific process is as follows:

[0068] 30mL of 0.67mol / L NaOH solution and 5mL of 2mol / L NaNO3 solution were taken into a 100mL conical flask to mix into the bottom liquid, then 20mL of 0.5mol / L FeSO4 solution was added, and the pH was adjusted to 11 with dilute sulfuric acid or sodium hydroxide solution; then the conical flask was tightly plugged with a rubber plug, and was placed in a 40℃ water bath, and the stirring speed was set to 500rpm, 600rpm, 700rpm, 800rpm, 900rpm and 1000rpm respectively, 100uL of oleic acid was added at the 2ndhour after the reaction started, and the Fe3O4crystals were enriched with a magnet after 5h of reaction, washed once with ethanol, then washed 3 times with deionized water, then centrifuged at 4000rpm for 3min, the supernatant was discarded, the precipitate was freeze-dried and then characterized.

[0069] By Figure 16 And Figure 17 It can be seen that when the stirring rate is 500-700rpm, the synthesized Fe3O4crystals have the best magnetism and hydrophobicity, and the difference is small; but when the stirring rate is above 600rpm, both the magnetism and the hydrophobicity have a weakening trend, so the optimal stirring rate is 500-700rpm.

[0070] Example 8

[0071] This example compares the effect of reaction time on the performance of the synthesized magnetic nanoparticles, and the specific process is as follows:

[0072] 30mL of 0.67mol / L NaOH solution and 5mL of 2mol / L NaNO3 solution were mixed into a 100mL conical flask to form a bottom solution, 20mL of 0.5mol / L FeSO4 solution was then added, and the pH was adjusted to 11 with dilute sulfuric acid or sodium hydroxide solution; then the conical flask was tightly plugged with a rubber plug, and was placed in a 40℃ water bath with a rotation speed of 700rpm, 100uL of oleic acid was added at the 2nd hour after the reaction started, and the reaction was carried out for 3h, 4h, 5h, 6h, 7h and 8h respectively, then the Fe3O4 crystals were enriched with a magnet, washed once with ethanol and three times with deionized water, and then centrifuged at 4000rpm for 3min, the supernatant was discarded, and the precipitate was freeze-dried for characterization.

[0073] It can be seen that the different reaction times have little effect on the magnetism of the Fe3O4 crystals, and the saturation magnetization is stable at about 85emu / g; but have a greater effect on the hydrophobicity, when the reaction time is 5h, the water contact angle is the largest, reaching 148.95°. Figure 18 Figure 19 It can be seen that the different reaction times have little effect on the magnetism of the Fe3O4 crystals, and the saturation magnetization is stable at about 85emu / g; but have a greater effect on the hydrophobicity, when the reaction time is 5h, the water contact angle is the largest, reaching 148.95°.

[0074] Comparative Example 1

[0075] This comparative example compares the magnetism and hydrophobicity of the Fe3O4 nanoparticles prepared in Example 8 of the present application and the Fe3O4 nanoparticles prepared by co-precipitation method in the literature (TIAN F et al. COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2020, 591: 124531). TIAN F et al. mixed Fe 3+ ions and Fe 2+ ions in a ratio of 2:1 (total iron mass of 6.76g), then slowly added ammonia and oleic acid into the mixture at a rate of 10 drops of ammonia and 1 drop of oleic acid, until 50ml of ammonia and 1ml of oleic acid were added. The mixture was stirred for 25min, and Fe3O4 precipitate was obtained. The saturation magnetization of the Fe3O4 nanoparticles prepared by TIAN F et al. was 55emu / g, and the water contact angle was 145.2°.

[0076] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application.

[0077] It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.​

Claims

1. A method for one-step low-temperature synthesis of strongly magnetic hydrophobic Fe3O4 nanoparticles, characterized in that, include: A ferrous salt solution was added to a mixed solution of sodium hydroxide and sodium nitrate, and the mixture was heated to 40-80℃ with stirring. Oleic acid was added during the reaction. After the reaction was complete, black Fe3O4 crystals were obtained. These crystals were centrifuged, washed, and freeze-dried to obtain strongly magnetic hydrophobic Fe3O4 nanoparticles. The initial pH of the reaction was 8-13, and the initial Fe content was... 2+ The concentration was 0.11-0.25 mol / L, and the initial NO3 concentration was... - The concentration is 0.18-0.55 mol / L; the oleic acid is added over a period of 1-3 hours and the dosage is 10-300 μL.

2. The method according to claim 1, characterized in that, The oleic acid is added over a period of 1-2 hours at a dosage of 100 μL.

3. The method according to claim 1, characterized in that, The ferrous salt is either ferrous sulfate or ferrous chloride.

4. The method according to claim 1, characterized in that, The initial NO3 of the reaction - The concentration was 0.18 mol / L; the initial Fe in the reaction was... 2+ The concentration is 0.18 mol / L.

5. The method according to claim 1, characterized in that, The initial pH of the reaction is 9-11.

6. The method according to claim 1, characterized in that, The stirring speed is 500-1000 rpm.

7. The method according to claim 6, characterized in that, The stirring speed is 500-700 rpm.

8. The method according to claim 1, characterized in that, The reaction time is 3-8 hours.

9. A strongly magnetic hydrophobic Fe3O4 nanoparticle prepared by the method according to any one of claims 1-8.

10. The application of the strongly magnetic hydrophobic Fe3O4 nanoparticles as described in claim 9 as an adsorbent in the treatment of oily wastewater.

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