阅读说明：本技术 Fe3O4@SiO2@ZnO:La磁性微球的制备方法及其应用 (Fe3O4@SiO2Preparation method and application of @ ZnO: La magnetic microspheres ) 是由 黄文艺 吕晓威 谭嘉麟 黄秋梅 邓丽娟 李利军 程昊 冯军 孔红星 李彦青 于 2019-10-29 设计创作，主要内容包括：本发明公开了Fe_3O_4@SiO_2@ZnO:La磁性微球的制备方法及其应用。本发明的磁性微球制备方法包括如下步骤：(1)Fe_3O_4的制备：采用溶剂热法合成Fe_3O_4微球；(2)Fe_3O_4@SiO_2的制备：采用反相微乳法制备得到单分散的Fe_3O_4@SiO_2微球；(3)Fe_3O_4@SiO_2@ZnO:La的制备：将Fe_3O_4@SiO_2微球分散在氯化锌和一定镧锌摩尔比的硝酸镧的混合溶液中,通过外部磁铁收集样品,然后再将收集的样品分散在六亚甲基四胺溶液中,搅拌反应,洗涤样品,真空干燥后收集得到。本发明制得的磁性微球的光催化性能优异,并且可重复使用,能够减少废水处理后材料产生的二次污染。(The invention discloses Fe 3 O 4 @SiO 2 A preparation method and application of @ ZnO: La magnetic microspheres. The preparation method of the magnetic microsphere comprises the following steps: (1) fe 3 O 4 The preparation of (1): synthesis of Fe by solvothermal method 3 O 4 Microspheres; (2) fe 3 O 4 @SiO 2 The preparation of (1): preparing monodisperse Fe by adopting a reverse microemulsion method 3 O 4 @SiO 2 Microspheres; (3) fe 3 O 4 @SiO 2 Preparation of @ ZnO: La: mixing Fe 3 O 4 @SiO 2 The microspheres are dispersed in a mixed solution of zinc chloride and lanthanum nitrate with a certain lanthanum-zinc molar ratio,collecting a sample by an external magnet, then dispersing the collected sample in a hexamethylenetetramine solution, stirring for reaction, washing the sample, and collecting after vacuum drying. The magnetic microsphere prepared by the invention has excellent photocatalytic performance, can be repeatedly used, and can reduce secondary pollution generated by materials after wastewater treatment.)

1.Fe₃O₄@SiO₂The preparation method of the @ ZnO: La magnetic microsphere is characterized by comprising the following steps of:

(1)Fe₃O₄the preparation of (1): synthesis of Fe by solvothermal method₃O₄Microspheres;

(2)Fe₃O₄@SiO₂the preparation of (1): preparing monodisperse Fe by adopting a reverse microemulsion method₃O₄@SiO₂Microspheres;

(3)Fe₃O₄@SiO₂preparation of @ ZnO: La: weighing 40mg of Fe₃O₄@SiO₂Dispersing microspheres in 60mL of mixed solution of zinc chloride and lanthanum nitrate, wherein the concentration of the zinc chloride in the mixed solution is 0.005-0.05M, the molar ratio of lanthanum to zinc is 0.5-5 mol%, fully stirring, collecting a sample through an external magnet, dispersing the collected sample in 60mL of 0.01-0.10M hexamethylenetetramine solution, carrying out water bath at 80-100 ℃, reacting under constant mechanical stirring, washing the sample, carrying out vacuum drying, and collecting Fe₃O₄@SiO₂@ ZnO: La magnetic microspheres.

2. Fe as claimed in claim 1₃O₄@SiO₂The preparation method of the @ ZnO: La magnetic microsphere is characterized by comprising the following steps: step (1) is to adopt an improved solvothermal method to synthesize Fe₃O₄The method comprises the following specific operation steps: dissolving 1.35g of ferric chloride hexahydrate in 40mL of ethylene glycol, stirring to obtain a clear solution, transferring the clear solution to a flask, carrying out water bath at 50-60 ℃, adding 1.0g of PEG4000 under constant mechanical stirring, stirring to dissolve for 30-60min, adding 3.6g of sodium acetate trihydrate, fully stirring to dissolve, transferring the reactant into a muffle furnace at 180 ℃ for 240 ℃ to react for 6-10h, cooling to room temperature, collecting a sample under the action of an external magnet, and alternately washing with ethanol and deionized waterThe sample is dried in a vacuum drying oven at 60 ℃ and collected to obtain Fe₃O₄And (3) microspheres.

3. Fe as claimed in claim 1₃O₄@SiO₂The preparation method of the @ ZnO: La magnetic microsphere is characterized by comprising the following steps: the specific operation steps of the step (2) are as follows: weighing 10mg of Fe prepared in the step (1)₃O₄Ultrasonically dispersing microspheres in 10-20mL of cyclohexane, and fully dispersing into a mixed solution A; measuring 1-2mL of Igepal CO-520, adding into 100mL of cyclohexane, ultrasonically dispersing for 10min, then dropwise adding the mixed solution A under constant mechanical stirring, quickly adding 1-2mL of 25% ammonia water and 12-20mL of deionized water after the dropwise addition of the mixed solution A is finished, and fully stirring for 2-4h to obtain a mixed solution B; adding 0.15-0.2mL of tetraethyl silicate into the mixed solution B at the speed of 30-100 mu L/24h to obtain Fe₃O₄@SiO₂Collecting the sample by an external magnet, alternately washing the sample by absolute ethyl alcohol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃, and collecting the sample to obtain Fe₃O₄@SiO₂And (3) microspheres.

4. Fe as claimed in claim 1₃O₄@SiO₂The preparation method of the @ ZnO: La magnetic microsphere is characterized by comprising the following steps: fe of the step (3)₃O₄@SiO₂Preparation of @ ZnO: La: 40mg of prepared Fe was weighed₃O₄@SiO₂Dispersing microspheres in 60mL of mixed solution of zinc chloride and lanthanum nitrate, wherein the concentration of zinc chloride in the mixed solution is 0.02M, the molar ratio of lanthanum to zinc is 5 mol%, stirring for 30min, collecting a sample through an external magnet, dispersing the sample in 60mL of 0.04M hexamethylenetetramine solution, carrying out water bath at 90 ℃, reacting for 3h under constant mechanical stirring, alternately washing the sample with ethanol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃, and collecting Fe₃O₄@SiO₂@ ZnO: La magnetic microspheres.

5. Any of claims 1 to 4Fe prepared by the preparation method₃O₄@SiO₂@ ZnO: La magnetic microspheres.

6. Fe as claimed in claim 5₃O₄@SiO₂The application of the @ ZnO: La magnetic microspheres as a magnetic photocatalyst in the aspect of wastewater treatment.

7. Fe of claim 6₃O₄@SiO₂The application of the @ ZnO: La magnetic microsphere as a magnetic photocatalyst in the aspect of treating wastewater is characterized in that: the treated wastewater is dye wastewater, and comprises the following steps:

s1, first treatment of wastewater: taking Fe₃O₄@SiO₂Adding the @ ZnO: La magnetic microspheres into the dye wastewater, wherein the ratio of the magnetic microspheres to the dye wastewater is 0.8 g: 40-60 mL; treating for 50-100min under the irradiation of low-pressure mercury lamp (300W, wavelength: 200-;

s2, repeated use of the magnetic photocatalyst: by subjecting the used Fe to deionized water₃O₄@SiO₂And after ultrasonically cleaning the @ ZnO: La magnetic microspheres, repeatedly using the magnetic microspheres according to the method in the step S1, wherein the repeated use times are more than or equal to 5 times.

Technical Field

The invention relates to the technical field of materials, in particular to Fe₃O₄@SiO₂A preparation method and application of @ ZnO: La magnetic microspheres.

Background

In recent years, semiconductor luminescent quantum dots are more and more emphasized by virtue of unique photoelectric characteristics, and have extremely wide application prospects in the fields of optoelectronic devices, biological fluorescent labeling and imaging, medical diagnosis, sensors, photocatalysis, functional anti-counterfeiting and the like. Among them, zinc oxide quantum dots are non-toxic, harmless, environment-friendly, and low in manufacturing cost, and have become a hotspot in the research field of optoelectronic materials and devices. At present, research on relevant technologies for doping zinc oxide quantum dots by rare earth lanthanum ions is carried out, but the research of the inventor finds that although the photocatalytic performance of the zinc oxide quantum dots can be enhanced by doping La with ZnO, the La-doped ZnO exists in a powder form and is difficult to separate after being used for treating wastewater, so that the waste of products is caused, and the cost of wastewater treatment is increased; and the La-doped ZnO in the treated wastewater can cause secondary pollution, which greatly limits the application of the La-doped ZnO in the photocatalytic treatment of dye wastewater.

With the rapid development of industrialization and urbanization, the environmental pollution problem is more serious, especially in the aspect of water pollution. Because water is the root for human beings and various living beings, no more life exists without good water resources, and the food chain relationship will change to some extent. Therefore, the water environment treatment is not slow, but the treatment at the present stage is basically carried out by adopting the traditional technology, so that secondary pollution can be generated to a certain extent, and the process and the material which are efficient, environment-friendly and energy-saving are especially important for degrading pollutants in water quality.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides Fe₃O₄@SiO₂A preparation method and application of @ ZnO: La magnetic microspheres. Fe prepared by the invention₃O₄@SiO₂The @ ZnO: La magnetic microspheres have excellent photocatalytic performance and can be repeatedly used, and secondary pollution generated by materials after wastewater treatment can be reduced.

In order to achieve the purpose, the technical scheme of the invention is as follows:

Fe₃O₄@SiO₂the preparation method of the @ ZnO: La magnetic microsphere comprises the following steps:

(1)Fe₃O₄the preparation of (1): synthesis of Fe by solvothermal method₃O₄Microspheres;

(2)Fe₃O₄@SiO₂the preparation of (1): preparing monodisperse Fe by adopting a reverse microemulsion method₃O₄@SiO₂Microspheres;

(3)Fe₃O₄@SiO₂preparation of @ ZnO: La: weighing 40mg of Fe₃O₄@SiO₂Dispersing microspheres in 60mL of mixed solution of zinc chloride and lanthanum nitrate, wherein the concentration of the zinc chloride in the mixed solution is 0.005-0.05M, the molar ratio of lanthanum to zinc is 0.5-5 mol%, fully stirring, collecting a sample by an external magnet, dispersing the collected sample in 60mL of 0.01-0.10M hexamethylenetetramine solution, and carrying out water bathReacting at 80-100 deg.C under constant mechanical stirring, washing sample, vacuum drying, and collecting to obtain Fe₃O₄@SiO₂@ ZnO: La magnetic microspheres.

Further, step (1) is to adopt the improved solvothermal method to synthesize Fe₃O₄The method comprises the following specific operation steps: dissolving 1.35g of ferric chloride hexahydrate in 40mL of ethylene glycol, stirring to obtain a clear solution, transferring the clear solution to a flask, carrying out water bath at 50-60 ℃, adding 1.0g of PEG4000 under constant mechanical stirring, stirring to dissolve for 30-60min, adding 3.6g of sodium acetate trihydrate, fully stirring to dissolve, transferring the reactant into a muffle furnace to react at 240 ℃ at 180 ℃ for 6-10h, cooling to room temperature, collecting a sample under the action of an external magnet, alternately washing the sample with ethanol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃, and collecting Fe₃O₄And (3) microspheres.

Further, the specific operation steps of the step (2) are as follows: weighing 10mg of Fe prepared in the step (1)₃O₄Ultrasonically dispersing microspheres in 10-20mL of cyclohexane, and fully dispersing into a mixed solution A; measuring 1-2mL of Igepal CO-520, adding into 100mL of cyclohexane, ultrasonically dispersing for 10min, then dropwise adding the mixed solution A under constant mechanical stirring, quickly adding 1-2mL of 25% ammonia water and 12-20mL of deionized water after the dropwise addition of the mixed solution A is finished, and fully stirring for 2-4h to obtain a mixed solution B; continuously adding 0.15-0.2mL of tetraethyl silicate into the mixed solution B at the speed of 30-100 mu L/24h under constant mechanical stirring to obtain Fe₃O₄@SiO₂Collecting the sample by an external magnet, alternately washing the sample by absolute ethyl alcohol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃, and collecting the sample to obtain Fe₃O₄@SiO₂And (3) microspheres.

Further, Fe of said step (3)₃O₄@SiO₂Preparation of @ ZnO: La: 40mg of prepared Fe was weighed₃O₄@SiO₂Dispersing the microspheres in 60mL of mixed solution of zinc chloride and lanthanum nitrate, wherein the concentration of the zinc chloride in the mixed solution is 0.02M, the molar ratio of lanthanum to zinc is 5 mol%, stirring for 30min, and passing through an external magnetCollecting a sample, then dispersing the sample in 60mL of 0.04M hexamethylenetetramine solution, reacting for 3h under constant mechanical stirring in a water bath at 90 ℃, alternately washing the sample with ethanol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃, and collecting Fe₃O₄@SiO₂@ ZnO: La magnetic microspheres.

The invention also provides the Fe₃O₄@SiO₂The application of the @ ZnO: La magnetic microspheres as a magnetic photocatalyst in the aspect of wastewater treatment.

Further, said Fe₃O₄@SiO₂The application of the @ ZnO: La magnetic microspheres as a magnetic photocatalyst in the aspect of treating wastewater, wherein the treated wastewater is dye wastewater, comprises the following steps:

s1, first treatment of wastewater: taking Fe₃O₄@SiO₂Adding the @ ZnO: La magnetic microspheres into the dye wastewater, wherein the ratio of the magnetic microspheres to the dye wastewater is 0.8 g: 40-60 mL; treating for 50-100min under the irradiation of low-pressure mercury lamp (300W, wavelength: 200-;

s2, repeated use of the magnetic photocatalyst: by subjecting the used Fe to deionized water₃O₄@SiO₂And (2) ultrasonically cleaning the @ ZnO: La magnetic microspheres, drying at 60 ℃, and then repeatedly using the magnetic microspheres according to the method in the step S1, wherein the repeated use times are more than or equal to 5.

The invention has the following advantages and technical effects:

binding of Fe according to the invention₃O₄@SiO₂Advantage of magnetic core-shell structure to prepare Fe₃O₄@SiO₂@ ZnO: La magnetic microsphere in which SiO₂The shell layer not only improves Fe₃O₄Chemical stability of the core, avoidance of agglomeration, and SiO₂A large amount of hydroxyl groups are exposed on the surface of the shell layer, so that the loading of ZnO to La particles can be promoted. Fe of the invention₃O₄@SiO₂The @ ZnO: La magnetic microsphere is not only excellent in photocatalytic performance, but also can be used for rapid separation and repeated use of a photocatalyst. Through tests, the invention

Fe₃O₄@SiO₂The degradation rate of the magnetic microsphere to methyl orange solution can still reach 81% after the magnetic microsphere is repeatedly used for five times, which indicates that the magnetic photocatalyst can be repeatedly utilized, and has great significance for fully utilizing resources, reducing the cost of treating dye wastewater and reducing secondary pollution in the wastewater treatment process.

Drawings

FIG. 1 shows different Zn²⁺Concentration produced Fe₃O₄@SiO₂SEM image of @ ZnO microsphere; wherein: (a)0.005M, (b)0.01M, (c)0.02M, (d) 0.05M;

FIG. 2 is a TEM and EDX image of a microsphere, wherein: (a) fe₃O₄TEM image of microspheres, (b) Fe₃O₄@SiO₂TEM image of microspheres, (c, d) Fe₃O₄@SiO₂TEM image of @ ZnO microspheres, (e) Fe₃O₄@SiO₂TEM image of @ ZnO: La microsphere, (f) Fe₃O₄@SiO₂EDX of @ ZnO: La microspheres;

FIG. 3 shows Fe before and after La doping₃O₄@SiO₂XPS full spectrum scan of @ ZnO microspheres;

FIG. 4 shows Fe before and after La doping₃O₄@SiO₂XPS spectrogram of @ ZnO microsphere-Zn 2 p;

FIG. 5 shows Fe before and after La doping₃O₄@SiO₂XPS spectrogram of @ ZnO microsphere-La 3 d;

FIG. 6 shows Fe before and after La doping₃O₄@SiO₂XPS spectrogram of @ ZnO microsphere-O1 s;

FIG. 7 is Fe₃O₄Microspheres of Fe₃O₄@SiO₂Microspheres of Fe₃O₄@SiO₂@ ZnO microspheres, Fe₃O₄@SiO₂A hysteresis loop diagram of the @ ZnO: La microsphere;

fig. 8 is a diagram showing a state in which microspheres are dispersed in water, wherein: (b) is Fe₃O₄@SiO₂@ ZnO: La microsphere, (c) Fe collected by external magnet₃O₄@SiO₂@ ZnO: La microspheres;

FIG. 9 shows different Zn²⁺Concentration produced Fe₃O₄@SiO₂A graph of the degradation rate of @ ZnO microspheres to methyl orange;

FIG. 10 shows different mol% of La doped with Fe₃O₄@SiO₂A graph of the degradation rate of @ ZnO microspheres to methyl orange;

FIG. 11 shows the reuse of Fe₃O₄@SiO₂Graph of influence of @ ZnO: La microspheres on degradation efficiency of methyl orange.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

1 reagents and instruments

Ferric chloride hexahydrate (Kyowa Kagaku chemical reagent Co., Ltd., Tianjin), cyclohexane, ethylene glycol (Kinghua Daichi chemical reagent Co., Ltd., Guangzhou), polyethylene glycol 4000, 25% ammonia water, sodium acetate trihydrate, zinc chloride, absolute ethanol, hexamethylenetetramine (Kangsu chemical Co., Ltd., Shanshou, Guangdong), polyoxyethylene (5) nonylphenyl ether, branched IgepalCO-520, and tetraethyl silicate (Aratidine reagent Co., Ltd.). All reagent specifications above were analytical grade and all water used in the experiment was deionized water.

Hitachi S-4800 field emission scanning electron microscope (Hitachi, Japan), JEM-2100 field emission transmission electron microscope (JEOL), MPMS-VSM and MPMS-XL vibrating sample magnetometer (Quantum Design, USA), SLX-1008 program controlled box resistance furnace (Hangzhou Tooth instruments Co., Ltd.), BPZ-6033LC vacuum drying box (Shanghai-Hengscience Co., Ltd.), UV-2102PC ultraviolet visible spectrophotometer (Shanghai Jiang instruments Co., Ltd.).

Preparation and application of 2 Fe3O4@ SiO2@ ZnO: La

(1)Fe₃O₄Preparation of

Improved solvothermal method for synthesizing Fe₃O₄Dissolving 1.35g of ferric chloride hexahydrate in 40mL of ethylene glycol, stirring to obtain a clear solution, transferring to a flask, adding 1.0g of PEG4000 under constant mechanical stirring in a water bath at 50 ℃, stirring to dissolve for 30min, adding 3.6g of sodium acetate trihydrate, and filling with the solutionStirring and dissolving, transferring the reactant into a high-temperature high-pressure reaction kettle, reacting for 8 hours at 200 ℃ in a muffle furnace, cooling to room temperature, collecting a sample under the action of an external magnet, alternately washing the sample with ethanol and deionized water, drying the washed sample for 2 hours at 60 ℃ in a vacuum drying oven, and collecting Fe₃O₄And (3) microspheres.

(2)Fe₃O₄@SiO₂Preparation of

Preparation of monodisperse Fe by reverse microemulsion method by controlling reaction conditions₃O₄@SiO₂Microspheres, 10mg of prepared Fe was weighed₃O₄Microspheres, ultrasonically dispersed in 10mL of cyclohexane, and fully dispersed into a mixed solution A. Measuring 1mL of Igepal CO-520, adding the Igepal CO-520 into 100mL of cyclohexane, ultrasonically dispersing for 10min, dropwise adding the mixed solution A under constant mechanical stirring, quickly (within 3 s) adding 2mL of 25% ammonia water and 18mL of deionized water after the dropwise adding of the mixed solution A, fully stirring for 2h to obtain a mixed solution B, continuously adding 0.2mL of tetraethyl silicate into the mixed solution B under constant mechanical stirring at the speed of 50 muL/24 h to obtain Fe₃O₄@SiO₂Collecting a sample by an external magnet, alternately washing the sample by absolute ethyl alcohol and deionized water, drying the washed sample in a vacuum drying oven at 60 ℃ for 2h, and collecting Fe₃O₄@SiO₂And (3) microspheres.

(3)Fe₃O₄@SiO₂Preparation of @ ZnO

40mg of prepared Fe was weighed₃O₄@SiO₂Dispersing the microspheres in 60mL zinc chloride solution (c is 0.005, 0.01, 0.02, 0.03, 0.04, 0.05M), stirring for 30min to make Zn²⁺Is fully adsorbed in Fe₃O₄@SiO₂The samples were collected on the microsphere surface by external magnet and then redispersed in 60mL of hexamethylenetetramine solution (c 0.01, 0.02, 0.04, 0.06, 0.08, 0.10M), reacted for 3h in a water bath at 90 ℃ under constant mechanical stirring, the samples were washed and dried for 2h in a vacuum oven at 60 ℃ to collect Fe₃O₄@SiO₂@ ZnO microspheres.

(4)Fe₃O₄@SiO₂Preparation of @ ZnO: La

40mg of prepared Fe was weighed₃O₄@ SiO2 microspheres were dispersed in 60mL of a mixed solution of zinc chloride and lanthanum nitrate (zinc chloride concentration 0.02M, lanthanum-zinc molar ratio 0.5 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%), stirred for 30min, a sample was collected by an external magnet, then dispersed in 60mL of a 0.04M hexamethylenetetramine solution, water bath 90 ℃, reacted for 3h under constant mechanical stirring, and washed with ethanol and deionized water alternately, the washed sample was dried in a vacuum drying oven at 60 ℃ for 2h, and Fe was collected₃O₄@SiO₂@ ZnO: La microspheres.

(5) The application of Fe3O4@ SiO2@ ZnO: La:

s1, first treatment of wastewater: taking Fe₃O₄@SiO₂Adding the @ ZnO: La magnetic microspheres into the dye wastewater, wherein the ratio of the magnetic microspheres to the dye wastewater is 0.8 g: 50 mL; treating for 50-100min under the irradiation of low-pressure mercury lamp (300W, wavelength: 200-;

s2, repeated use of the magnetic photocatalyst: by subjecting the used Fe to deionized water₃O₄@SiO₂And (2) ultrasonically cleaning the @ ZnO: La magnetic microspheres, drying at 60 ℃, and then repeatedly using the magnetic microspheres according to the method in the step S1, wherein the repeated use times are more than or equal to 5.

3 photocatalytic Performance test

Weighing 0.8g of magnetic microspheres in a quartz test tube, adding 50mL of 3mg/L methyl orange solution, sampling once at intervals of 20min under the irradiation of a low-pressure mercury lamp (300W, wavelength: 200-. Standard curve of concentration C (mg/L) of methyl orange at test wavelength 465nm versus absorbance A:

A＝0.0599*C+0.0012

the formula for calculating the degradation rate D of methyl orange is as follows:

D＝(C₀-C_t)/C₀*100

in the formula C₀And C_tInitial and light concentration after time t, respectively.

4 analysis of test results

And after the SEM sample is subjected to gold spraying treatment, an SEM image of the sample is obtained under the scanning voltage of 5-15 KV. And ultrasonically dispersing TEM sample powder in absolute ethyl alcohol to form suspension, impregnating the suspension in a copper net, drying at room temperature, and testing to obtain a TEM image of the sample. XPS samples were fixed on conducting gel and pressed into thin sheets for testing. The hysteresis loop of the samples was recorded using VSM with an electric field of-5000 to 5000Oe applied at room temperature.

By adjusting Zn²⁺The concentration can be controlled and adsorbed in Fe₃O₄@SiO₂Amount of ZnO nanoparticles on the surface of the microspheres. FIG. 1 is Zn²⁺Fe prepared at concentrations of 0.005, 0.01, 0.02, 0.05M, respectively₃O₄@SiO₂SEM image of @ ZnO microspheres, Fe₃O₄@SiO₂The amount of the nano ZnO attached to the surface of the microsphere is along with Zn²⁺The concentration increases. However, Zn²⁺Too high a concentration may cause agglomeration of ZnO nanoparticles, which in d of fig. 1 agglomerate into irregular shapes, which will greatly limit the photocatalytic activity of the ZnO nanoparticles. Thus remaining attached to Fe when preparing reusable photocatalyst₃O₄@SiO₂On the premise that the ZnO nanoparticles on the surfaces of the microspheres have good dispersibility, the amount of the ZnO nanoparticles directly influences Fe₃O₄@SiO₂@ ZnO microsphere's photocatalytic properties.

The invention carries out more structural detail analysis on the core-shell structure of the magnetic core, as shown in figure 2, wherein a is Fe₃O₄TEM image of microspheres, Fe₃O₄The microspheres are monodisperse cores. In order to make the structure more stable, SiO is adopted₂Fe prepared as shell material₃O₄@SiO₂The microspheres are shown in b of FIG. 2, as can be clearly seen in Fe₃O₄Core-shell two-component structure as core, to obtain more obvious structural details, compare the enlarged view of 20nm scale, in Fe₃O₄Nuclear bagCoated with about 20nm of SiO₂And (4) shell layer. C and d in FIG. 2 are Zn²⁺Fe prepared at concentrations of 0.02 and 0.05M, respectively₃O₄@SiO₂@ ZnO microsphere, clearly seen in Fe₃O₄@SiO₂ZnO particles attached to the surface of the microsphere, and Zn²⁺Fe prepared at a concentration of 0.05M₃O₄@SiO₂The amount of ZnO particles in the @ ZnO microspheres was significantly increased, however, there was an agglomeration phenomenon of the attached ZnO particles. Wherein SiO is caused by the adhesion of ZnO particles₂The shell cannot be clearly shown in the TEM images. In FIG. 2, e is Fe₃O₄@SiO₂The TEM image of the @ ZnO: La microsphere can obviously see the nanoparticles attached to the surface, but the doping of La does not obviously change the morphology and the particle size of ZnO particles, and the comparison result shows that Fe₃O₄@SiO₂The TEM images of the @ ZnO microspheres did not differ significantly. It was therefore characterised by EDX, whose EDX spectrum is shown in f of FIG. 2, in which not only Fe, O, Si, Zn are present, but also La, indicating Fe₃O₄@SiO₂The nano particles adhered to the surfaces of the @ ZnO: La microspheres are ZnO: La particles. In addition, in Fe₃O₄@SiO₂@ ZnO microsphere and Fe₃O₄@SiO₂In TEM images of the @ ZnO: La microspheres, there is a phenomenon that part of nanoparticles fall off, which may be related to ultrasonic dispersion of a sample before testing, and the falling off phenomenon is also an important reason that photocatalytic efficiency is reduced when the magnetic photocatalyst is repeatedly used.

FIGS. 3-6 are Fe before and after La doping₃O₄@SiO₂XPS plot of @ ZnO microspheres with Fe₃O₄@SiO₂XPS plot of @ ZnO as reference to analyze La incorporation versus Fe₃O₄@SiO₂@ ZnO microspheres. As can be seen from the XPS full spectrum scan of the magnetic microsphere in FIG. 3, Fe is doped₃O₄@SiO₂The XPS graph of the @ ZnO microsphere shows a diffraction peak of La, which indicates that La is successfully doped with Fe₃O₄@SiO₂@ ZnO microspheres. FIG. 4 is an XPS spectrum of Zn 2p with an energy difference of 23eV between two diffraction peaks of Zn 2p3/2 and Zn 2p1/2, indicating that Zn is mainly represented by Zn²⁺Does not alter the Zn 2p peak by doping with La, indicating that the incorporation of La does not alter Zn in ZnO²⁺The existence form of (2) and the adhesion of ZnO to Fe₃O₄@SiO₂The surface of the microsphere does not influence the chemical property of ZnO. FIG. 5 is an XPS spectrum of La 3d with two peaks at 835eV and 852eV, La 3d5/2 and La 3d3/2, respectively, indicating that La is in the form of La³⁺The spin-orbit splitting distance of the La 3d peak is 17eV, and the peak is matched with other La-doped hosts, and a satellite peak exists on the higher energy side due to the degree of mixing of the 4f electron layer of the lanthanide compound and the extended conduction band state. FIG. 6 is an XPS spectrum of O1 s with Fe before and after La doping using Gaussian fitting analysis₃O₄@SiO₂Deconvolution of O1 s spectra of @ ZnO microspheres to lie at 520.5eV (O)₁)，531.6eV(O₂)，532.3eV(O₃) And 533.2eV (O)₄) Of (a), wherein O₁Lattice oxygen, O, ascribed to ZnO₂Is SiO₂Oxygen of medium Si-O bond, O₃Is Fe₃O₄Of (a) lattice oxygen, and O₄Related to the hydroxyl and oxygen defects on the surface of the microsphere. In Fe₃O₄@SiO₂In @ ZnO microspheres O₄About 27.8% in Fe₃O₄@SiO₂@ ZnO: La microsphere O₄About 31.0%, indicating Fe₃O₄@SiO₂La microspheres can adsorb more surface hydroxyl groups, the hydroxyl groups promote the formation of OH free radicals through light induction holes, and the La doping can effectively improve Fe due to the fact that the attack of high-activity OH free radicals on model molecules can promote photocatalytic degradation reaction₃O₄@SiO₂@ ZnO microsphere's photocatalytic properties.

As shown in FIG. 7, is Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ ZnO and Fe₃O₄@SiO₂The hysteresis loop of the @ ZnO: La microsphere is shown in FIG. 7, and the prepared magnetic microsphere shows good ferromagnetism at room temperature, wherein Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ ZnO and Fe₃O₄@SiO₂The magnetic saturation intensities (Ms) of the @ ZnO: La microspheres were 92, 61, 54 and 52emu/g, respectively. Due to SiO₂Presence of a shell layer, Fe₃O₄@SiO₂The Ms value of the microspheres decreased significantly, while the Ms value of the magnetic microspheres decreased again after the nanoparticles were deposited. And the Ms value of the magnetic photocatalyst has no obvious change before and after doping La, which shows that the doped La has little influence on the ferromagnetism of the magnetic photocatalyst. B in FIG. 8 is Fe₃O₄@SiO₂Picture of La microballon dispersed in water, this magnetic microballon has good dispersibility in water. Under the action of an external magnet, the magnetic microspheres can be magnetized within a few seconds, are rapidly separated from water, and leave a clear solution (such as c in fig. 8), which shows that the magnetic photocatalyst can be not only fully dispersed in water, but also can be rapidly collected under the action of the magnet, and can be applied to the reuse and rapid separation of the photocatalyst.

5 photocatalytic Properties

5.1 different Zn²⁺Concentration produced Fe₃O₄@SiO₂Photocatalytic performance of @ ZnO microspheres

FIG. 9 shows different Zn²⁺Concentration produced Fe₃O₄@SiO₂The degradation rate curve of @ ZnO microspheres to 50mL of 3mg/L methyl orange simulated water sample. As can be seen from the graph, the degradation rate of the sample on the methyl orange is increased along with the increase of the time, the degradation rate of the photocatalyst on the methyl orange is faster within 0-20min, and the degradation rate tends to be flat within 20-100 min. With Zn²⁺Increase in concentration, Fe₃O₄@SiO₂The degradation rate of the @ ZnO microspheres to methyl orange is increased and then reduced, and Zn is added²⁺The maximum is reached at a concentration of 0.02M, and the degradation rate of methyl orange is 88%. This is due to the presence of Zn²⁺At a low concentration, the dispersibility of ZnO particles is good, and Zn is²⁺The concentration increase will be in Fe₃O₄@SiO₂The amount of ZnO particles attached to the microspheres is increased, the specific surface area is increased, and the photocatalytic performance is improved, but with Zn²⁺Increased concentration of Fe₃O₄@SiO₂ZnO particles attached to the microspheres are saturated and then attached to Fe₃O₄@SiO₂ZnO particles on the microsphere are agglomerated into irregular shapes, so that the specific surface area of the microspheres is reduced, and Fe is reduced₃O₄@SiO₂@ ZnO microsphere's photocatalytic properties. This is also demonstrated in connection with fig. 1, where the agglomerated ZnO particles can be clearly seen in d of fig. 1. Thus by controlling Zn²⁺Concentration, regulation of adhesion to Fe₃O₄@SiO₂The amount of ZnO particles on the microspheres can effectively improve Fe₃O₄@SiO₂The @ ZnO microsphere has the photocatalytic performance, and the maximum utilization of raw materials can be realized.

5.2 different mol% La doping vs. Fe₃O₄@SiO₂Influence of @ ZnO microsphere photocatalytic performance

As shown in FIG. 10, different mol% of La was doped with Fe₃O₄@SiO₂The degradation rate curve of @ ZnO microspheres to 50mL of 3mg/L methyl orange. With the increase of La doping amount, Fe₃O₄@SiO₂The photocatalytic efficiency of the @ ZnO: La microspheres to methyl orange is increased. At 80min, 5 mol% of La is doped with Fe₃O₄@SiO₂The degradation rate of the @ ZnO microspheres to methyl orange reaches 93 percent, and the methyl orange is basically completely degraded; and Fe not doped with La₃O₄@SiO₂The degradation rate of the @ ZnO microsphere to methyl orange is 80%, which indicates that the La doping can effectively improve Fe₃O₄@SiO₂@ ZnO microsphere's photocatalytic properties.

5.3Fe₃O₄@SiO₂Repeated use of @ ZnO: La microspheres

In order to examine the reusability of the prepared magnetic photocatalyst, the photocatalytic performance test condition is maintained (0.8 g of magnetic microspheres are weighed in a quartz test tube, 50mL of 3mg/L methyl orange solution is added, the sample is sampled once every 20min under the irradiation of a low-pressure mercury lamp (300W, wavelength: 200-400nm) in a photochemical reaction instrument after 30min of a dark box, the sample is separated by an external magnet, the absorbance of the sample supernatant is measured, and the concentration of methyl orange and the standard of the absorbance are determinedAnd calculating the degradation rate of the magnetic microspheres to the methyl orange solution by using a standard curve. ) The change of the photocatalytic performance of the used magnetic photocatalyst in the process of repeated use is evaluated by the degradation efficiency of the photocatalyst on methyl orange by repeatedly using 50mL of 3mg/L methyl orange solution after the magnetic photocatalyst is ultrasonically cleaned and dried by deionized water. FIG. 11 shows Fe with a degradation time of 100min and a La doping amount of 5 mol%₃O₄@SiO₂In the process of reusing the microspheres for 5 times, the change curve of the degradation rate of 50mL of 3mg/L methyl orange shows that the degradation efficiency of the magnetic photocatalyst on the methyl orange is reduced along with the repeated use, which is probably caused by Fe₃O₄@SiO₂@ ZnO: La microspheres are subjected to ultrasonic cleaning, and a small part of ZnO particles fall off. But Fe₃O₄@SiO₂The decomposition rate of methyl orange can still reach 81% after the @ ZnO: La microspheres are repeatedly used for 5 times, which shows that the magnetic photocatalyst can be repeatedly utilized, and has great significance for fully utilizing resources and reducing the cost of treating dye wastewater.

In conclusion, the invention successfully prepares the Fe with the stable core-shell structure by a chemical liquid phase reaction method₃O₄@SiO₂The @ ZnO: La microsphere integrates multiple functions of the magnetic core and the shell. The experimental result shows that in the preparation of Fe₃O₄@SiO₂@ ZnO, too high or too low Zn²⁺The concentration of Zn in the solution can reduce the photocatalytic activity of the solution²⁺When the concentration is 0.02M, the photocatalytic activity of the photocatalyst is the best; when the La doping amount is 0-5 mol%, the increase of the La doping concentration can enhance Fe₃O₄@SiO₂The @ ZnO: La microsphere has photocatalytic performance, and the magnetic photocatalyst still has good degradation efficiency on methyl orange after being repeatedly used for 5 times. The magnetic photocatalyst not only has excellent photocatalytic performance, but also can be used for quick separation and repeated use of the photocatalyst, so that the magnetic photocatalyst has great advantages in reducing the cost of treating dye wastewater and reducing secondary pollution in the wastewater treatment process.

Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.