阅读说明：本技术 一种纳米氧化镁的制备方法，其产品和应用 (Preparation method of nano magnesium oxide, product and application thereof ) 是由 林松 刘士胜 于 2021-04-08 设计创作，主要内容包括：本发明涉及环境保护及净化领域,具体讲,涉及一种纳米氧化镁的制备方法,其产品和应用。本发明提出一种纳米氧化镁的制备方法,包括以下步骤：采用甲醇镁为原料,制备得到氢氧化镁溶胶；将氢氧化镁溶胶以恒定升温速率加热至130～155℃,并保温,得到氢氧化镁凝胶；烧结氢氧化镁凝胶,得到纳米氧化镁。本发明提供的纳米氧化镁的制备方法高效、快速、节能；能够制备得到粒径较小、比表面积大且粒径分布均匀的纳米氧化镁；本发明的纳米氧化镁降解对氧磷和吸附Pb(II)等重金属离子效果优异。(The invention relates to the field of environmental protection and purification, in particular to a preparation method of nano magnesium oxide, a product and application thereof. The invention provides a preparation method of nano magnesium oxide, which comprises the following steps: preparing magnesium hydroxide sol by using magnesium methoxide as a raw material; heating the magnesium hydroxide sol to 130-155 ℃ at a constant heating rate, and preserving heat to obtain magnesium hydroxide gel; and sintering the magnesium hydroxide gel to obtain the nano magnesium oxide. The preparation method of the nano magnesium oxide provided by the invention is efficient, rapid and energy-saving; the nano magnesium oxide with small particle size, large specific surface area and uniform particle size distribution can be prepared; the nano-magnesia has excellent effects of degrading paraoxon and adsorbing heavy metal ions such as Pb (II) and the like.)

1. A preparation method of nano magnesium oxide at least comprises the following steps:

s1, preparing magnesium hydroxide sol by using magnesium methoxide as a raw material;

s2, heating the magnesium hydroxide sol to 130-155 ℃ at a constant heating rate, preserving heat to obtain magnesium hydroxide wet gel, and drying to obtain magnesium hydroxide gel;

the constant heating rate refers to the fluctuation value of the heating rate being less than 1 ℃;

and S3, sintering the magnesium hydroxide gel to obtain the nano magnesium oxide.

2. The method according to claim 1, wherein the magnesium hydroxide sol is prepared by:

s11, dissolving magnesium methoxide in an organic solvent to obtain a magnesium methoxide solution; the mass percentage concentration of the magnesium methoxide solution is 5-12%, and the preferable mass percentage concentration is 7-10%;

s12, sequentially adding the magnesium methoxide solution into an organic phase and an aqueous phase under the protection of nitrogen, and reacting for 8-24 hours at 10-25 ℃ to obtain magnesium hydroxide sol;

the organic phase is preferably a benzene solvent, preferably toluene or xylene, and the aqueous phase is preferably deionized water.

3. The method according to claim 2, wherein the organic solvent is preferably an alcoholic solvent, more preferably methanol;

preferably, the volume ratio of the magnesium methoxide solution to the organic phase is 1: 3-1: 10, preferably 1: 2.4-1: 3.25.

4. the method according to claim 2, wherein the volume ratio of the magnesium methoxide solution to the aqueous phase is 15: 1-40: 1; preferably 20: 1-34: 1;

preferably, the deionized water is added dropwise.

5. The method according to any one of claims 1 to 4, wherein in S2, microwaves are used to keep the temperature rise rate constant and the temperature constant during the heat preservation, preferably, the power of the microwaves fluctuates within a range of 0 to 400W;

preferably, the heating time is 10-40 min, the heating rate is 3-15 ℃/min, and the heat preservation time is 10-30 min;

more preferably, the pressurization during heating is performed to keep the temperature rise rate constant, and preferably, the pressure fluctuates within 0 to 3 MPa.

6. The method according to any one of claims 1 to 4, wherein in S3, the sintering temperature is 400 to 700 ℃, preferably 450 to 600 ℃, and more preferably 500 ℃;

the sintering time is 8-24 hours, preferably 9-18 hours, and more preferably 10-12 hours.

7. The nano magnesium oxide prepared by the preparation method according to any one of claims 1 to 6.

8. The nano-magnesia as claimed in claim 7, wherein the nano-magnesia has a particle size of 3 to 40nm and a specific surface area of 40 to 400m²/g。

9. The use of the nano-magnesia according to claim 8 for environmental cleaning.

10. The use of claim 9, wherein the use comprises degrading paraoxon and removing heavy metal ions from water.

Technical Field

The invention relates to the field of environmental protection and purification, in particular to a preparation method of nano magnesium oxide, a product and application thereof.

Background

The smaller the particle of the nano magnesium oxide is, the more unsaturated bonds, edge and corner 'defects' and ionized groups on the surface are, and the stronger the adsorption and degradation acting force with organic poisons is. However, the smaller the nano magnesium oxide particles, the more aggregation is likely to occur, and there is a certain inconvenience in use. Hydrothermal method refers to a method for preparing materials by dissolving and recrystallizing powder in a sealed pressure vessel with water as a solvent. Compared with other powder preparation methods, the powder prepared by the hydrothermal method has the advantages of complete crystal grain development, small granularity, uniform distribution, light particle agglomeration, use of cheaper raw materials, easy obtainment of proper stoichiometric matters and crystal forms and the like. In particular, the hydrothermal method for preparing the ceramic powder does not need high-temperature calcination treatment, and the growth of crystal grains, defect formation and impurity introduction caused in the calcination process are avoided, so that the prepared powder has higher sintering activity. However, the conventional hydrothermal method has long time for preparing crystal grains, high energy consumption and low industrialization and cost reduction. Therefore, it is necessary to develop a high-efficiency, rapid and energy-saving nano-magnesia preparation process and method.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a method for preparing nano magnesium oxide.

The second invention aims to provide the nano-magnesia prepared by the method.

The third invention of the invention aims to provide the application of the nano-magnesia.

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

the invention provides a preparation method of nano magnesium oxide, which at least comprises the following steps:

s1, preparing magnesium hydroxide sol by using magnesium methoxide as a raw material;

s2, heating the magnesium hydroxide sol to 130-155 ℃ at a constant heating rate, preserving heat to obtain magnesium hydroxide wet gel, and drying to obtain magnesium hydroxide gel;

the constant heating rate refers to the fluctuation value of the heating rate being less than 1 ℃;

and S3, sintering the magnesium hydroxide gel to obtain the nano magnesium oxide.

The second aspect of the invention provides the preparation methodThe prepared nano-magnesia has the particle size of 3-40 nm and the specific surface area of 40-400 m²/g。

The third aspect of the invention provides the application of the nano-magnesia in environmental purification, which comprises degrading paraoxon and removing heavy metal ions in water.

The invention has at least the following beneficial effects:

the preparation method of the nano magnesium oxide provided by the invention is efficient, rapid and energy-saving; the nano magnesium oxide with small particle size, large specific surface area and uniform particle size distribution can be prepared; the nano-magnesia has excellent effects of degrading paraoxon and adsorbing heavy metal ions such as Pb (II) and the like.

Drawings

FIG. 1 is a transmission electron microscope image of nano-magnesia prepared in example 1 of the present invention;

FIG. 2 is a particle size histogram of the nano-magnesia prepared in example 1 of the present invention;

FIG. 3 is an adsorption isotherm diagram (FIG. a) and a cumulative porosity profile (FIG. b) of nano-magnesia prepared in example 1 of the present invention;

FIG. 4 is a transmission electron microscope image of nano-magnesia prepared in example 3 of the present invention;

FIG. 5 is a particle size histogram of the nano-magnesia prepared in example 3 of the present invention;

FIG. 6 is an adsorption isotherm diagram (FIG. a) and a cumulative porosity profile (FIG. b) of nano-magnesia prepared in example 3 of the present invention.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise, and further, it is understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, devices, components, and/or combinations thereof.

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention innovatively adopts magnesium methoxide as the starting material, provides the preparation method of the nano magnesium oxide, has the technical advantages of high efficiency, high speed and energy conservation, and can prepare the nano magnesium oxide with small particle size, large specific surface area and uniform particle size distribution. The method comprises the following steps:

s1, preparing magnesium hydroxide sol by using magnesium methoxide as a raw material;

s2, heating the magnesium hydroxide sol to 130-155 ℃ at a constant heating rate, preserving heat to obtain magnesium hydroxide wet gel, and drying to obtain magnesium hydroxide gel; the constant heating rate means that the fluctuation value of the heating rate is less than 1 ℃;

and S3, sintering the magnesium hydroxide xerogel to obtain the nano magnesium oxide.

In one embodiment, the preparation method of the magnesium hydroxide sol comprises the following steps:

s11, dissolving magnesium methoxide in an organic solvent to obtain a magnesium methoxide solution;

and S12, sequentially adding the magnesium methoxide solution into an organic phase and a water phase under the protection of nitrogen, reacting for 8-24 hours at 10-25 ℃, and hydrolyzing, aging and standing to obtain magnesium hydroxide sol and obtain the magnesium hydroxide sol.

Wherein the mass percentage concentration of the magnesium methoxide solution is 5-12%, and the preferable mass percentage concentration is 7-10%; if the mass percent concentration of the magnesium methoxide solution is too large, the amount of water required by the reaction is correspondingly increased, and the generated magnesium hydroxide is likely to be converted into precipitate from a gel state because the amount of toluene is constant; too little will reduce the yield and more energy will be required to produce the same quality product.

In particular, the organic phase is preferably a benzene-based organic solvent, preferably toluene and xylene, and the aqueous phase is preferably deionized water. The interaction between the hydroxyl group and the benzene series solvent is helpful for protecting the gel structure. This allows the surface area of the final product to be further increased.

In particular, the organic solvent is preferably an alcoholic solvent, and may be selected from methanol, ethanol, ethylene glycol and glycerol, and more preferably methanol, which has a low boiling point and is easily removed. Secondly, methanol is a byproduct in the reaction process, and the use of methanol can avoid introducing impurities again.

In particular, the volume ratio of the magnesium methoxide solution to the organic phase is 1: 2-1: 10, preferably 1: 2.4-1: 3.25. if the organic phase is added too little, the specific surface area of the produced product is smaller; if the organic phase is added too much, the specific surface area of the final product is not further increased. Only a certain amount of organic solvent can obtain the optimum specific surface area.

In particular, the volume ratio of magnesium methoxide solution to aqueous phase is 15: 1-40: 1; preferably 20: 1-34: 1; if the water phase is added too much, the magnesium hydroxide will be transformed from sol state to precipitate; if the amount of the aqueous phase is too small, the reaction of magnesium methoxide will be incomplete, resulting in a low yield. The aqueous phase addition therefore requires a suitable amount.

Preferably, the aqueous phase is added dropwise. If the addition rate is too high, magnesium methoxide and water directly form large particles of magnesium hydroxide, which precipitate, and thus magnesium hydroxide sol cannot be formed. The aqueous phase addition cannot be too fast.

According to the embodiment of the invention, the wet magnesium hydroxide gel is filtered to obtain the filter cake. The embodiment of the present invention does not particularly limit the specific implementation of the filtration, and the filtration method known to those skilled in the art may be adopted. The embodiment of the invention washes the filter cake obtained by filtering. The washing detergent preferably comprises one or more of water, methanol, ethanol and toluene. The embodiment of the present invention is not particularly limited to the specific washing method, and the washing method known to those skilled in the art may be used. Vacuum drying is preferred for embodiments of the present invention in which drying is performed. The benefits of vacuum drying are: the microstructure of the gel is not damaged, and the grain diameter and the surface area of the nano magnesium oxide are ensured.

In one embodiment, in S2, the microwave is used to keep the temperature raising rate constant and the temperature during the heat preservation constant, but those skilled in the art may also use other temperature raising methods, and it is only necessary to keep the temperature raising rate constant and the temperature during the heat preservation constant. The specific operation can adopt a microwave chemical synthesizer, and after the heating rate and the heat preservation temperature are set, the equipment can automatically adjust the power according to the temperature of the solvent to keep the heating rate and the heat preservation temperature constant. The power of the microwave fluctuates within 0-400W, and the specific numerical value can also be changed according to different instrument models.

Wherein the constant heating rate means that the fluctuation value of the heating rate is less than 1 ℃; preferably less than 0.5 deg.c, more preferably less than 0.2 deg.c, and most preferably less than 0.1 deg.c.

The final temperature rise is 130-155 ℃, preferably 135-155 ℃, and most preferably 150-155 ℃.

Wherein the heating rate is 3-15 ℃/min, preferably 5-10 ℃/min, and the heating time is 10-40 min. The temperature increase rate is kept constant, which means that the temperature is increased to a predetermined temperature at the temperature increase rate during the entire temperature increase process after the temperature increase rate is selected within the range. The solution can be uniformly heated by keeping the temperature rise speed constant, the gel structure of the product is protected, the necessity of keeping the temperature constant during heat preservation is to enable the hydrothermal reaction to be more sufficient, and meanwhile, the product has enough time for nucleation and growth. If the temperature is raised too fast, the conversion of magnesium hydroxide from the sol state to the gel state may be incomplete. If the temperature rising speed is too slow, the specific surface area of the obtained final product is not ideal, the energy consumption is larger, and the energy is not saved. The purpose of the heat preservation is to allow the reaction to proceed sufficiently, and the magnesium hydroxide in the gel state is better dispersed in the solvent. The reaction is incomplete due to too short time, the specific surface area of the final product obtained by too long time is not ideal, the energy consumption is larger, and the energy is not saved.

Preferably, the heat preservation time is 10-30 min; the purpose of the heat preservation is to enable the hydrothermal reaction to be more complete and enable the product to have enough time for nucleation and growth.

More preferably, the pressure is increased during heating to keep the rate of temperature rise constant, and the pressure detected by the apparatus is 0MPa in the initial heating stage. When the heating is continued, the pressure begins to rise slowly and finally tends to be stable. The pressure can fluctuate within 0-3 MPa, and the specific numerical value can also change according to different types of instruments.

In one embodiment, in S3, the sintering is vacuum sintering, and is preferably performed in a vacuum tube furnace; the sintering temperature is 400-700 ℃, preferably 450-600 ℃, and further preferably 500 ℃; the sintering time is 8-24 h, preferably 9-18 h, more preferably 10-12 h, and further preferably 10 h. If the temperature is too low, incomplete calcination may be caused, and if the temperature is too high, the particle size and specific surface area of the magnesium oxide may be adversely affected.

The embodiment of the invention also relates to the nano magnesium oxide prepared by the preparation method.

Preferably, the nano-magnesia has a particle size of 3-40 nm and a specific surface area of 40-400 m²In one embodiment, the particle size of 70% by number of the nano-sized magnesium oxide particles is in the range of 10 to 40nm, and in another embodiment, the particle size of 70% by number of the nano-sized magnesium oxide particles is in the range of 4 to 10 nm.

The embodiment of the invention also relates to the application of the nano magnesium oxide in environmental purification, which comprises degrading oxygen phosphorus and removing heavy metal ions in water, wherein the oxygen phosphorus is preferably ethyl paraoxon, and the heavy metal ions comprise Pb and Cd. The method of the present invention is not particularly limited, and any method known to those skilled in the art may be used.

The degradation process of the nano magnesium oxide and paraoxon molecules is a catalytic decomposition and conjugated adsorption process. The adsorption removal of Pb and Cd ions is a chemical reaction, and the reaction formula is as follows:

MgO+H₂O→Mg(OH)₂

Cd²⁺+Mg(OH)₂→Cd(OH)₂+Mg²⁺

Cd²⁺+CO₂+H₂O→CdCO₃+2H⁺

3Pb²⁺+Mg(OH)₂+2CO₂+2H₂O→Pb₃((CO)₃)₂(OH)₂+Mg²⁺+4H⁺

MgO+Pb²⁺→PbO+Mg²⁺

MgO+Cd²⁺→CdO+Mg²⁺

specifically, the preparation method of the nano magnesium oxide in the embodiment of the invention comprises the following steps:

s1, dissolving magnesium methoxide in methanol to obtain an alcoholic solution; the concentration of the magnesium methoxide in the alcoholic solution is 5 to 12 weight percent; preparation of a magnesium methoxide alcohol solution in N₂Under protection, sequentially adding a certain proportion of toluene and deionized water, and hydrolyzing, aging and standing to obtain magnesium hydroxide sol; wherein the dosage of the magnesium methoxide is 30-100 mL, the dosage of the methylbenzene is 100-300 mL, and the dosage of the deionized water is 1-5 mL;

s2, performing microwave-assisted hydrothermal treatment on the magnesium hydroxide sol to obtain nano magnesium hydroxide; the product is further filtered, washed and dried to obtain magnesium hydroxide gel; the heating temperature is 25-180 ℃, the heating rate is 3-15 ℃/min, the heating time is 10-40 min, and the heat preservation time is 10-30 min. In the processes of temperature rise and heat preservation, the power of the microwave fluctuates within 0-400W, the power of the microwave is 0-400W, and the pressure in the closed autoclave fluctuates within 0-3 MPa; after the microwave hydrothermal reaction is finished, cooling the product, and further filtering, washing and drying the product to obtain magnesium hydroxide gel;

s3, sintering the magnesium hydroxide gel in a vacuum tube furnace to obtain nano magnesium oxide; the sintering temperature is 400-700 ℃, and the sintering time is 10-24 h. Obtaining the nano magnesium oxide.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The sources and types of reagents and instruments used in this example: magnesium methoxide (7-8 wt.%, Shanghai Alatin Biotechnology Co., Ltd.), toluene (analytical purity, Tianjin Maotai chemical reagent factory), deionized water (18.0M Ω), a multipurpose microwave chemical synthesizer (XH-300UP, Beijing auspicin scientific and technological development Co., Ltd.), a field emission transmission electron microscope (2010FEF, Japan JEOL Co., Ltd.), and a full-automatic specific surface and porosity analyzer (TriStar II 3020, USA Mike instruments Co., Ltd.). Other reagents are commercially available unless otherwise specified.

Example 1

First, 50mL of 7 wt% Mg (OCH)₃)₂Added to 120mL of toluene and magnetically stirred, and 1.5mL of deionized water was added dropwise to the above solution. Finally reacting at room temperature overnight to obtain the hydrolysate as gel Mg (OH)₂. Filtered and washed two to three times.

The resulting gelled Mg (OH)₂The product is put into a closed autoclave of a microwave chemical synthesizer, and the initial temperature is 25 ℃, the final temperature is 150 ℃, the temperature rise time is 20min, the heat preservation time is 20min, and the temperature rise rate is 6.25 ℃/min are directly input into an instrument operation interface by adopting a multi-purpose microwave chemical synthesizer. In the processes of temperature rise and heat preservation, the microwave power fluctuates within the range of 0-400W, and the pressure in the closed autoclave fluctuates within the range of 0-3 MPa. After the microwave hydrothermal reaction is finished, washing the product for 3-4 times by using methanol after cooling and suction filtration, drying the product in a drying oven overnight, and then calcining the product by using a vacuum tube furnace: the calcining temperature is 500 ℃, the calcining time is 10 hours, and the sample is taken out after cooling to obtain the nano-magnesia.

The nano-magnesia obtained in example 1 was analyzed by transmission electron microscopy, and the transmission electron microscopy image is shown in fig. 1. As can be seen from FIG. 1, the nano-magnesia provided by the present invention has small particle size and uniform distribution. The nano-magnesia particle size data was obtained by using image J in fig. 1 and using a particle size statistic n of 50, the particle size statistic graph is shown in fig. 2, and the data is shown in table 1.

TABLE 1 particle size distribution table of nano-magnesia prepared in inventive example 1

As can be seen from Table 1, the nano-magnesia provided by the invention has small particle size and relatively uniform distribution.

The adsorption isotherm diagram and the cumulative porosity profile of the nano-magnesia obtained in example 1 are shown in FIG. 3, and the specific surface area of the nano-magnesia calculated from FIG. 3 is 213.5m²/g。

Example 2

First, 40mL of 10 wt% Mg (OCH)₃)₂Added to 130mL of toluene and magnetically stirred, and then 2mL of deionized water was added dropwise to the above solution. Finally reacting at room temperature overnight to obtain the hydrolysate as gel Mg (OH)₂. Filtered and washed two to three times. The resulting gelled Mg (OH)₂The product is put into a closed autoclave of a microwave chemical synthesizer, and the initial temperature of 25 ℃, the final temperature of 155 ℃, the temperature rise time of 30min, the heat preservation time of 30min and the temperature rise rate of 4.83 ℃/min are directly input into an operation interface of the instrument by adopting a multi-purpose microwave chemical synthesizer. In the temperature rise and heat preservation processes, the microwave power fluctuates within the range of 0-400W, and the pressure in the closed high-pressure kettle fluctuates within the range of 0-3 MPa. After the microwave hydrothermal reaction is finished, washing the product for 3-4 times by using methanol after cooling and suction filtration, drying the product in a drying oven overnight, and then calcining the product by using a vacuum tube furnace: the calcining temperature is 450 ℃, the calcining time is 9 hours, and the sample is taken out after cooling to obtain the nano-magnesia.

And (3) performing transmission electron microscope analysis on the nano-magnesia obtained in the example 2, wherein the transmission electron microscope image is similar to that of the example 1, and the nano-magnesia with small particle size and uniform step by step is obtained.

Example 3

First, 50mL of 12 wt% Mg (OCH)₃)₂Added to 150mL of toluene and magnetically stirred, and 2.5mL of deionized water was added dropwise to the above solution. Finally reacting at room temperature overnight to obtain the hydrolysate as gel Mg (OH)₂. Filtered and washed two to three times.The resulting gelled Mg (OH)₂The product is put into a closed autoclave of a microwave chemical synthesizer, and the initial temperature of 25 ℃, the final temperature of 140 ℃, the temperature rise time of 40min, the heat preservation time of 30min and the temperature rise rate of 3.625 ℃/min are directly input into an instrument operation interface by adopting a multi-purpose microwave chemical synthesizer. In the temperature rise and heat preservation processes, the microwave power fluctuates within the range of 0-400W, and the pressure in the closed high-pressure kettle fluctuates within the range of 0-3 MPa. After the microwave hydrothermal reaction is finished, washing the product for 3-4 times by using methanol after cooling and suction filtration, drying the product in a drying oven overnight, and then calcining the product by using a vacuum tube furnace: the calcining temperature is 600 ℃, the calcining time is 12 hours, and the sample is taken out after cooling to obtain the nano-magnesia.

And (3) performing transmission electron microscope analysis on the nano-magnesia obtained in the example 3, wherein the transmission electron microscope image of the example 3 is similar to the transmission electron microscope image of the example 1, and the nano-magnesia with small particle size and uniform step by step is obtained. The nano-magnesia particle size data was obtained by using image J in fig. 4, and the particle size data is shown in fig. 5 and table 2, respectively.

TABLE 2 particle size distribution table of nano-magnesia prepared in example 3 of the present invention

As can be seen from Table 2, the nano-magnesia provided by the present invention has large particle size and relatively dispersed distribution.

The adsorption isotherm diagram and the cumulative porosity profile of the nano-magnesia obtained in example 3 are shown in FIG. 6, and the specific surface area of the nano-magnesia calculated from FIG. 6 is 46.78m²/g。

Example 4:

1. the preparation was carried out by the method of example 1, with the difference that: when the final temperature is 190 ℃ directly input into the operation interface of the multipurpose microwave chemical synthesizer, the reaction inner tank and the pressure-resistant outer tank are damaged in the experimental process. While the corresponding product is still available, the relevant parameters are not considered to be a safe and safe operation.

2. The preparation was carried out by the method of example 1, with the difference that: when the final temperature is 160 ℃ directly input into the operation interface of the multipurpose microwave chemical synthesizer, the operation is repeated twice, wherein magnetons in the tank are damaged in the experimental process once, and iron in the magnetons is dissolved into the solution, so that reactants are polluted.

Therefore, it was found through the above experiment that the upper limit of the temperature for microwave heating was selected to be 155 ℃.

Example 5:

1. the preparation was carried out by the method of example 2, with the difference that: the temperature of calcination was 450 ℃. The test finds that: the magnesium oxide sample produced was impure with a small amount of magnesium hydroxide present.

2. The preparation was carried out by the method of example 2, with the difference that: the temperature of calcination was 600 ℃. The test finds that: the prepared magnesium oxide has larger particle size which is counted as 20-60 nm, and smaller specific surface area which is calculated as 40-50 m²/g。

Experimental example 1

Application example 1: the degradation performance of the nano-magnesia prepared in example 1 was tested by the following methods: 0.005g of nano-magnesia was added to 10mL of a 3.2mg/L solution of ethyl paraoxon, and the change in absorbance with time at 268nm was measured to calculate the degradation rate. Wherein the ethyl paraoxon solution is obtained by dissolving ethyl paraoxon in n-heptane. Similarly, the nano-magnesia of examples 2-3 are labeled as application example 2 and application example 3, respectively. The test results are shown in table 3.

Meanwhile, commercially available nano magnesium oxide (with a particle size of 20nm (nominal)) is adopted as a comparative example 1 (purchased from Nanjing Xiancheng nano materials science and technology Co., Ltd., with a particle size of 20nm and a specific surface area of 42.05m²In terms of/g), the experiment was carried out in the same manner as described above. The test results are shown in table 3.

TABLE 3 degradation rate of paraoxon by nano-magnesia

As can be seen from the test results in Table 3, the effect of the nano magnesium oxide provided by example 1 of the present invention in degrading paraoxon is better and much higher than the effect of the nano magnesium oxide provided by example 2, example 3 and comparative example 1 in degrading paraoxon.

Experimental example 2

Application example 4: weighing a certain mass of lead acetate (Pb (CH)₃COO)₂·3H₂O) is dissolved in deionized water to prepare the concentration of 50mg L^-1The Pb (II) solution of (2) was prepared by adding 5mg of commercially available nano-magnesium oxide and the nano-magnesium oxide prepared in example 1 to 20mL or more of the solution, respectively. Then oscillating at room temperature, taking supernatant at different time intervals (5, 10, 60, 120min), and detecting Pb in the supernatant by using inductively coupled plasma mass spectrometer²⁺The concentration of (c).

Meanwhile, commercially available nano magnesium oxide (with a particle size of 20nm (nominal)) is adopted as a comparative example 2 (purchased from Nanjing Xiancheng nano materials science and technology Co., Ltd., with a particle size of 20nm and a specific surface area of 42.05m²In terms of/g), the experiment was carried out in the same manner as described above. The test results are shown in table 4.

TABLE 4 adsorption rate of nano-magnesia on heavy metal ions Pb (II)

In conclusion, the nano magnesium oxide prepared by the method provided by the invention has smaller particle size and uniform particle size distribution, and the effect of degrading paraoxon by the nano magnesium oxide is effectively improved. In addition, the nano magnesium oxide provided by the invention has a good effect of degrading paraoxon, and the degradation rate can reach 68.15% after 90min of degradation. The removal effect on heavy metals is also good, and after the adsorption is carried out for 60min, the removal rate reaches 97.15 percent, which are all superior to the nano magnesium oxide samples sold in the market.

Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.