CN109589933B - Magnetic nano composite material UiO-66/Fe3O4Preparation method and application of/GO - Google Patents

Abstract

The invention relates to a magnetic nano composite material UiO-66/Fe₃O₄A preparation method and application of/GO belong to the technical field of composite materials. UiO-66/Fe is synthesized by one-step synthesis₃O₄Anchoring the nano-microspheres on a GO sheet layer to obtain UiO-66/Fe₃O₄a/GO magnetic nanocomposite. The composite material prepared by the method overcomes the defects that graphene sheets are easy to stack and Fe is easy to generate₃O₄The nano particles are easy to agglomerate, and the nano cavities and Cs thereof⁺The radius has good compatibility. The adsorbent is used for adsorbing Cs in water⁺And excellent adsorption performance is shown. UiO-66 modified by magnetic material and GO not only for Cs⁺Has good adsorbability, and the material is easy to separate due to the magnetism of the material. Therefore, the invention has the characteristics of simple preparation process, good stability, high adsorption efficiency, easy solid-liquid separation, easy recovery, environmental protection and the like.

Description

Preparation method and application of a magnetic nanocomposite material UiO-66/Fe3O4/GO

technical field

The invention belongs to the technical field of composite materials, and relates to a preparation method of a magnetic nano-composite material UiO-66/Fe ₃ O ₄ /GO and the application of the material to the adsorption and removal of Cs ⁺ in an aqueous solution.

Background technique

With the increase of global energy demand and the enhancement of environmental protection awareness, carbon-free nuclear power, as a key alternative energy source for fossil fuels, plays an important role in the development of human society. However, the disposal of radioactive waste in nuclear fission still limits the development of carbon-free nuclear power. Among them, radioactive cesium ( ¹³⁷ Cs) is the radioactive material produced by fission, accounting for 6.3% of the fission products. It is the leading cause of radioactive contamination and the most abundant species in nuclear power plant accidents and nuclear waste disposal. Radioactive cesium is a strong source of gamma radiation with a long half-life (T _1/2 = 30.17 years), similar to the biogeochemical behavior of potassium. It is highly mobile and poses a serious threat to the environment and human health through its continuous flow through the food chain. Therefore, before long-term storage of nuclear waste, radioactive ions must be eliminated to reduce the radioactivity below the allowable range. Various processing techniques have been used to remove the radionuclide cesium from aqueous solutions with high adsorption efficiency, simplicity, flexibility and affordability. The adsorption process does not use any toxic organic solvents. However, many of these adsorbents are not reproducible and are often associated with environmental hazards. Therefore, efficient and low-cost materials should be sought to selectively remove cesium-containing wastewater.

UiO-66 as a three-dimensional porous zirconium-based MOF composed of a 1,4-phthalic acid linker and a cationic _Zr6O4 (OH _{)4 node} with octahedral and tetrahedral cavities, is characterized by its excellent thermal stability The advantages of chemical properties, water stability, acid stability, and ease of synthesis have received great attention. However, UiO-66 usually exists in powder form and is not conducive to isolation from solution. Magnetic separation can quickly and easily separate solid materials from liquids. _Fe3O4 magnetic nanoparticles have been widely studied due to their low production cost, easy preparation and large _- scale production capability. However, magnetic nanomaterials possess magnetic properties and large active surfaces, and the strong interparticle interactions among magnetic nanoparticles make them difficult for further applications. The immobilization of magnetic nanoparticles _on substrates is a feasible method to stabilize _Fe3O4 nanoparticles and reduce aggregation. Graphene oxide is an ideal platform for the formation of new composites because of its hydrophilicity and availability of hydroxyl, epoxy and carbocyclic groups, which enable excellent dispersion in solution. In addition, GO can also be used as an adsorbent. _Fe3O4 magnetic nanoparticles anchored _on GO. The magnetization of the sorbent matrix facilitates the recovery of the used sorbent and provides a simple and feasible solution for the removal of target species from solution. And the composite material prepared by the method of the invention overcomes the shortcomings of easy stacking of graphene sheets and easy agglomeration of Fe ₃ O ₄ nanoparticles, and the nano cavity has good compatibility with the Cs ⁺ radius. The adsorption of Cs ⁺ in water with this adsorbent showed excellent adsorption performance. The UiO-66 modified with magnetic material and GO not only has good adsorption to Cs ⁺ , but also the separation is quite easy due to the magnetic properties of the material itself.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a magnetic nanocomposite material which is simple to operate, easy to separate, green and environmentally friendly, and can be used for adsorbing Cs ⁺ . The invention synthesizes a magnetic nano-composite material UiO-66/Fe ₃ O ₄ /GO, using GO as a carrier, Fe ₃ O ₄ as a core, UiO-66 as a shell, and UiO-66/Fe ₃ O ₄ small balls The UiO-66/Fe ₃ O ₄ /GO nanocomposite was obtained by anchoring on the GO sheet, which can be applied to the adsorption and removal of Cs ⁺ in aqueous solution.

A preparation method of magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO, comprising the following steps:

(1) Take graphene oxide and place it in N,N-dimethylformamide solution, ultrasonic for 5-8 hours, and the ultrasonic power is 300W, so that the graphene oxide solid is fully dissolved in the N,N-dimethylformamide solution middle;

(2) adding ferric oxide particles after the graphene oxide is fully dissolved, and ultrasonically treating for 10 minutes to obtain a mixed solution;

(3) adding the zirconium tetrachloride powder into the above-mentioned mixed solution for ultrasonic treatment for 30 minutes, followed by mechanical stirring for 12 hours, and the mechanical stirring speed is 200 rpm;

(4) add terephthalic acid powder after mechanical stirring, continue stirring for 30 minutes;

(5) the treated mixed solution is loaded into the stainless steel autoclave with polytetrafluoroethylene lining, and the autoclave is heated to 120 ° C, and the reaction is maintained for 24 hours;

(6) after the reaction, cooled to room temperature, filtered, the solid was washed with ethanol and deionized water, and separated from the solution by magnetic separation, and finally, the obtained black solid was freeze-dried to obtain the magnetic nanocomposite UiO-66/Fe ₃ O ₄ /GO.

The ratio of ethanol to deionized water is 1:1, and the washing is performed more than 3 times.

The composite material prepared by the invention is used for the adsorption of radioactive substances; the radioactive substances are Cs ⁺ .

The advantages of the present invention are:

(1) The composite material prepared by the method of the present invention overcomes the shortcomings of easy stacking of graphene sheets and easy agglomeration of Fe ₃ O ₄ nanoparticles, and its nano-cavity has good compatibility with Cs ⁺ radius. The adsorbent can adsorb Cs ⁺ in water, showing excellent adsorption performance;

(2) Compared with UiO-66/GO modified by magnetic material and UiO-66/GO without GO modification, UiO-66/Fe ₃ O ₄ modified with magnetic material and GO not only has good adsorption to Cs ⁺ , and also due to the magnetic properties of the material itself, its separation is quite easy.

(3) the present invention has the characteristics of simple preparation process, good stability, high adsorption efficiency, easy solid-liquid separation, easy recovery and green environmental protection;

(3) The magnetic nanocomposite UiO-66/Fe ₃ O ₄ /GO prepared by the present invention takes GO as a carrier and has the characteristics of good acid and alkali resistance, thermal stability and easy solid-liquid separation.

Description of drawings

Figure 1(a) is a scanning electron microscope image of the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2, and Figure 1 (b) is the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2. TEM image, Figure 1(c) is the scanning electron microscope image of the UiO-66/Fe ₃ O ₄ /GO composite prepared in Example 3, and Figure 1(d) is the UiO-66/Fe prepared in Example 3 TEM image of the ₃ O ₄ /GO composite.

Figure 2(a) is the hysteresis curve diagram of the UiO-66/Fe ₃ O ₄ /GO composite prepared in Example 3, and Figure 2(b) is the UiO-66/Fe ₃ O ₄ / Comparison of the effect before and after magnetic separation of GO composites.

Figure 3 shows the UiO-66 solid material prepared in Example 1, the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2 and the UiO-66/Fe ₃ O ₄ /GO composite material prepared in Example 3 Adsorption efficiency curves for Cs ⁺ at different initial concentrations of Cs ⁺ .

Figure 4 shows the UiO-66 solid material prepared in Example 1, the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2 and the UiO-66/Fe ₃ O ₄ /GO composite material prepared in Example 3 The adsorption efficiency curves for Cs ⁺ at different adsorption times.

Figure 5 shows the UiO-66 solid material prepared in Example 1, the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2 and the UiO-66/Fe ₃ O ₄ /GO composite material prepared in Example 3 Adsorption efficiency curves for Cs ⁺ at different temperatures.

Figure 6 shows the UiO-66 solid material prepared in Example 1, the UiO-66/Fe ₃ O ₄ composite material prepared in Example 2 and the UiO-66/Fe ₃ O ₄ /GO composite material prepared in Example 3 Adsorption efficiency curves for Cs ⁺ under different pH conditions.

Detailed ways

The present invention will be described in detail below with reference to the embodiments in order to better understand the objects, features and advantages of the present invention. Although the invention is described in conjunction with the specific embodiment, it is not intended to be limited to the specific embodiment described. On the contrary, alternatives, improvements and equivalent embodiments to the embodiments that can be included in the protection scope defined in the claims of the present invention fall within the protection scope of the present invention. For process parameters that are not specially marked, conventional techniques can be used.

The embodiment of the present invention provides a magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO for adsorbing Cs ⁺ in an aqueous solution.

Example 1:

Preparation of UiO-66

Dissolve 0.386g zirconium tetrachloride powder and 0.276g terephthalic acid powder in N,N-dimethylformamide solution, pour into a 100mL reaction kettle after forming a uniform mixed solution, and heat at 120°C for 24h, Naturally cooled to room temperature and then centrifuged, washed with ethanol and deionized water for several times, and freeze-dried to obtain a white powder that is UiO-66 solid.

Example 2:

Preparation of Magnetic Nanocomposites UiO-66/Fe ₃ O ₄

Immerse 0.1 g of ferric oxide particles into 40 mL of N,N-dimethylformamide solution, and perform ultrasonic treatment for 30 minutes to obtain a mixed solution of ferric tetroxide. In addition, 0.15 g of zirconium tetrachloride powder and 0.1062 g of terephthalic acid powder were sequentially added to 30 mL of N,N-dimethylformamide solution and sonicated for 10 minutes to obtain a MOF precursor solution. The mixed solution of ferric tetroxide was poured into the MOF precursor solution and sonicated until the solid particles were uniformly dispersed in the solution. The homogeneously mixed solution was poured into a 100 mL autoclave, placed in an oven at 80°C for 12 hours, and then placed at 100°C for 24 hours. The resulting light brown solid was washed several times with ethanol and deionized water and separated from solution by magnetic separation. The purified UiO _- 66/ _Fe3O4 composite solid was obtained by freeze-drying.

Example 3:

Preparation of Magnetic Nanocomposites UiO-66/Fe ₃ O ₄ /GO

Take 0.03 g of graphene oxide and place it in 80 mL of N,N-dimethylformamide solution, and ultrasonicate for 5-8 hours to fully dissolve it. After the graphene oxide was fully dissolved, 0.075 g of ferric oxide particles were added and ultrasonically treated for 10 minutes. Then, 0.1125 g of zirconium tetrachloride powder was added to the above mixed solution and sonicated for 30 minutes, followed by mechanical stirring for 12 hours. Finally, 0.0797 g of terephthalic acid powder was added to it, and stirring was continued for 30 minutes. The treated mixed solution was put into a 100 mL stainless steel autoclave with a polytetrafluoroethylene lining, and the autoclave was heated to 120° C. to maintain the reaction for 24 hours. After cooling to room temperature, filtered, the synthesized solid was washed several times with ethanol and deionized water, and separated from solution by magnetic separation. Finally, the obtained black solid was freeze-dried to obtain UiO-66/Fe ₃ O ₄ /GO nanocomposite. Its saturation magnetization is 15.53 emu·g ^-1 , as shown in Fig. 2(a).

In addition, it can be seen from Figure 1(a) and Figure 1(b) that graphene oxide is a sheet structure with many wrinkles, and UiO _- 66/ _Fe3O4 nanoparticles are attached to the graphene oxide sheet in a spherical shape. layer.

Adsorption performance test

The materials prepared in Examples 1, 2, and 3 were applied to the determination of Cs ⁺ adsorption performance, as follows:

计算。其中C₀和C_e(mg·L^-1)分别是初始和平衡时Cs⁺浓度，m(g)是吸附剂的质量，V(L)是Cs⁺溶液的体积。如图3所示，吸附量q_e随着初始Cs⁺浓度的升高而增加，并且在初始Cs⁺浓度为80mg·L^-1时分别获得57.29mg·g^-1，59.93mg·g^-1和62.07mg·g^-1的平衡容量。UiO-66/Fe₃O₄/GO的吸附能力高于UiO-66 和UiO-66/Fe₃O₄，因为GO的加入增加了材料的表面积，提供了更多的活性部位与Cs⁺反应。在低浓度下，Cs⁺的竞争力相对低于其他阳离子。随着Cs⁺浓度的提升，Cs⁺与其他阳离子的竞争力增强，使其能够占据吸附位点直至饱和。当达到平衡时，吸附和解吸处于动态平衡，导致吸附能力不再增加，甚至可能随着浓度的增加而降低。Adsorb 50.0 mL of Cs ⁺ solution in a 50-ml sealed Erlenmeyer flask with 0.01 g of adsorbent, and control the temperature and rotation speed by a water bath shaker to keep the rotation speed at 200 rpm. The residual Cs ⁺ concentration was measured using an atomic absorption spectrophotometer (nov AA 300). To reduce experimental error, three parallel tests were performed simultaneously in each experiment. The mass of Cs ⁺ adsorbed per unit mass of adsorbent can be obtained by the formula

calculate. where C ₀ and _Ce (mg·L ^-1 ) are the initial and equilibrium Cs ⁺ concentrations, respectively, m(g) is the mass of the adsorbent, and V(L) is the volume of the Cs ⁺ solution. As shown in Fig. 3, the adsorption amount q _e increased with the increase of the initial Cs ⁺ concentration, and 57.29 mg·g ^-1 and 59.93 mg·g ^-1 were obtained when the initial Cs ⁺ concentration was 80 mg·L ^-1 , respectively. and an equilibrium capacity of 62.07 mg·g ^-1 . The adsorption capacity of UiO-66/Fe ₃ O ₄ /GO is higher than that of UiO-66 and UiO-66/Fe ₃ O ₄ , because the addition of GO increases the surface area of the material and provides more active sites to react with Cs ⁺ . At low concentrations, Cs ⁺ is relatively less competitive than other cations. As the concentration of Cs ⁺ increases, the competitiveness of Cs ⁺ with other cations increases, enabling it to occupy adsorption sites until saturation. When equilibrium is reached, adsorption and desorption are in dynamic equilibrium, resulting in no increase in adsorption capacity, and may even decrease with increasing concentration.

The change in adsorption capacity of adsorbents with different contact times was investigated. Under the conditions of a temperature of 298K and a pH of 7, 0.01 g of the adsorbents prepared in Examples 1, 2, and 3 were weighed and added to 50 mL of Cs ⁺ solution with an initial concentration of 60 mg·L ^-1 . Oscillation for different times at a speed of 200 rpm. With the increase of time, the adsorption capacity of the adsorbent for Cs ⁺ gradually increased, and finally the adsorption was saturated. The research results are shown in Figure 4. The synthesized adsorbent has a fast adsorption rate and an equilibrium time of 2 h.

In order to study the effect of temperature on the adsorption properties of the composites, 0.01 g of the adsorbents prepared in Examples 1, 2, and 3 were added to 50 mL of an initial concentration of 60 mg·L ^-1 at different temperatures of 298K, 308K, 318K and 328K. In the Cs ⁺ solution, the pH was controlled to be 7, and a constant temperature oscillator was used to keep the rotation speed at 200 rpm and the temperature at 298 K for 12 h. The results are shown in Fig. 5, indicating the endothermic reaction characteristics of the adsorption process and the thermal stability of the adsorbent.

The pH value of the solution is one of the important factors affecting the adsorption performance of the adsorbent. Weigh 0.01g of the adsorbent prepared in Examples 1, 2, and 3, add it to 50mL of Cs ⁺ solution with an initial concentration of 60mg·L ^-1 , adjust the pH to 4-9 with 0.1M HCl or NaOH, and use a constant temperature oscillator. Keep the rotation speed at 200rpm and the temperature at 298K and shake for 12h. As shown in Fig. 6, the adsorbent UiO-66/Fe ₃ O ₄ /GO reached the maximum adsorption capacity q _e at pH 8.

It must be emphasized that the above-mentioned embodiments are only examples for clearly illustrating the present invention, but the present invention is not limited to the above-mentioned embodiments. Those of ordinary skill in the art can also make other changes in different forms on the basis of the above description. It is impossible and unnecessary to give examples for all implementations here, but the obvious changes derived from this are still within the scope of the present invention. protected range.

Claims (5)

1. a magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO is used for the application of adsorbing radioactive material Cs, it is characterized in that: The preparation method of the magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO includes the following steps: (1) Take graphene oxide and place it in N,N-dimethylformamide solution, ultrasonic for 5-8 hours, so that graphene oxide solid is fully dissolved in N,N-dimethylformamide solution; (2) After the graphene oxide is fully dissolved, the ferric oxide particles are added, and ultrasonically treated to obtain a mixed solution; (3) Add zirconium tetrachloride powder to the above mixed solution for ultrasonic treatment, followed by mechanical stirring; (4) After mechanical stirring, add terephthalic acid powder and continue stirring; (5) Put the treated mixed solution into a PTFE-lined stainless steel autoclave, heat the autoclave to 120°C, and maintain the reaction for 24 hours; (6) After the reaction, cooled to room temperature, filtered, the solid was washed with ethanol and deionized water, and separated from the solution by magnetic separation, and finally, the obtained black solid was dried to obtain the magnetic nanocomposite UiO-66/Fe ₃ O ₄ /GO. 2 . The application of the magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO for adsorbing radioactive material Cs according to claim 1 , wherein the ultrasonic power is 300W. 3 . 3. The application of the magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO for adsorbing radioactive material Cs according to claim 1, wherein the mechanical stirring speed of step (3) is 200 rpm, and the stirring speed is 200 rpm. The time is 12 hours. 4. The application of the magnetic nanocomposite UiO-66/Fe ₃ O ₄ /GO for adsorbing radioactive material Cs according to claim 1, characterized in that the quality of ethanol and deionized water described in step (6) The ratio is 1:1, and it is washed more than 3 times. The application of the magnetic nanocomposite material UiO-66/Fe ₃ O ₄ /GO for adsorbing radioactive material Cs according to claim 1, characterized in that the drying described in step (6) is freeze-drying.

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