CN114177888B

CN114177888B - Preparation of GO/COFs composite material and application of GO/COFs composite material in organic pollutant adsorption

Info

Publication number: CN114177888B
Application number: CN202111350115.XA
Authority: CN
Inventors: 陈佳; 梁丽; 邱洪灯
Original assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Current assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-11-01
Anticipated expiration: 2041-11-15
Also published as: CN114177888A

Abstract

The invention discloses a preparation method of a graphene oxide/covalent organic frameworks (GO/COFs) composite material, which comprises the steps of mixing 1,3, 5-tris (4-aminophenyl) benzene and acetic acid, adding an acetonitrile solution, dissolving solids by ultrasonic waves, adding a graphene oxide suspension, and stirring for 5 to 30 min to obtain a uniform dispersion liquid; and then adding an acetonitrile solution of 2, 5-divinyl-1, 4-benzene dicarboxaldehyde into the uniform dispersion liquid, violently shaking in a vortex mixer to uniformly mix the mixture, standing at room temperature for 2 to 72 hours, washing an obtained green precipitate crude product with tetrahydrofuran and ethanol, and drying to obtain the GO/COFs composite material. The composite material is used for adsorbing organic pollutants, and has good adsorption capacity and reusability on organic pollutants naphthalene, 1-naphthylamine and 1-naphthol.

Description

Preparation of GO/COFs composite material and application of GO/COFs composite material in organic pollutant adsorption

Technical Field

The invention belongs to the technical field of composite material preparation, and relates to a preparation method of a GO/COFs composite material; and also relates to the application of the composite material in the adsorption of organic pollutants.

Background

In recent years, with the continuous development of industrialization, various organic pollutants are discharged into water environment in large quantity due to strong toxicity, high carcinogenicity and nondegradable property, and great attention is paid to people. Organic pollutants widely exist in the environment, including pharmaceutical, petrochemical, dye, pesticide and other industrial wastewater, and even if the organic pollutants are exposed at low concentration, the organic pollutants can also pose certain threats to human survival and ecological environment. Therefore, organic contaminants must be disposed of before being released into the environment. How to rapidly treat and reduce the concentration of organic pollutants in a solution is a hot point for water treatment research. In recent years, a great deal of research has been conducted by many researchers on the remediation of organic pollutants. The method for effectively removing the persistent organic pollutants in the aqueous solution comprises an oxidation method, a natural degradation method, a bioremediation method, an adsorption method and the like. Wherein, the oxidation method is easy to cause secondary pollution, and the natural degradation method and the bioremediation method have the defects of long time consumption and low removal rate. However, adsorption technology is widely used due to its advantages of simple operation, low cost, availability of a variety of adsorbent materials, no environmental toxicity, ease of design, etc. Therefore, it is very important to prepare an adsorbent with large adsorption capacity, good stability and reusability.

Disclosure of Invention

The invention aims to provide a preparation method of a GO/COFs (graphene oxide/covalent organic framework) composite material;

another object of the present invention is the use of GO/COFs composites in the adsorption of organic pollutants.

Preparation and structure of (I) GO/COFs composite material

The invention discloses a method for preparing GO/COFs composite material, which comprises the following steps: firstly, mixing 1,3, 5-tris (4-aminophenyl) benzene and acetic acid, adding an acetonitrile solution, performing ultrasonic treatment to dissolve solids, adding a Graphene Oxide (GO) suspension, and stirring for 5 to 30 min to obtain a uniform dispersion liquid; and then adding an acetonitrile solution of 2, 5-divinyl-1, 4-benzene dicarboxaldehyde into the uniform dispersion liquid, violently shaking in a vortex mixer to uniformly mix the materials, standing at room temperature for 2 to 72 hours, washing an obtained green precipitate crude product with tetrahydrofuran and ethanol, and drying to obtain the GO/COFs composite material.

The molar ratio of the 1,3, 5-tris (4-aminophenyl) benzene to acetic acid is 1. The molar ratio of the 1,3, 5-tris (4-aminophenyl) benzene to 2, 5-divinyl-1, 4-benzenedicarboxaldehyde is 2. The mass ratio of the total mass of the 1,3, 5-tri (4-aminophenyl) benzene and the 2, 5-divinyl-1, 4-benzene dicarbaldehyde to the graphene oxide is 1.

FIG. 1 is a Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images of GO, COFs and GO/COFs, as shown in FIG. 1a, GO has a lamellar morphology with slight wrinkles. As shown in FIGS. 1b and 1 c, COFs exhibit rough spherical surfaces with a diameter of about 800 nm. FIG. 1d is a TEM image of GO/COFs, from which both GO folds and COFs morphology can be seen. FIG. 1e is a high resolution TEM image of GO/COFs, from which it can be clearly seen that the open framework diameter of COFs is about 2.6 nm. FIG. 1f is the distribution diagram of GO/COFs elements, and it can be seen that the elements C, N and O are uniformly distributed. This confirms the successful synthesis of GO/COFs composites.

FIG. 2a is the XRD pattern of GO/COFs composite material prepared as described above, and it can be seen from the figure that the GO/COFs composite material is 2.78^oA strong peak appears at 4.82, 5.57, 7.40, 9.57, and 25.85^oThere are several relatively weak peaks, which are consistent with those of COFs, but the intensity is reduced, because the presence of GO, but in a lower amount, does not show up in GO/COFs, which further confirms the successful synthesis of GO/COFs composites.

FIG. 2b is FT-IR of GO/COFsAs can be seen, GO has the following characteristic functional groups, alkoxy C-O (1049 cm)⁻¹) Epoxy group C-O-C (1384 cm)⁻¹) Aromatic C = C (1631 cm)⁻¹) And a C = O (1721 cm "1) bond. COFs have the following characteristic functional groups C = N (1596 cm)⁻¹)，N-H (3437 cm⁻¹)，C=O (1691 cm⁻1) The appearance of C = N demonstrates that the condensation reaction of the amino group of TPB with the aldehyde group of DVA is successful. It can be clearly observed that GO/COFs not only have the characteristic functional groups of GO C-O, but also the characteristic functional groups of COFs: c = N, which further confirms the successful synthesis of GO/COFs composites.

FIG. 3a is a thermogravimetric graph of GO/COFs composite material, and it can be seen that the composite material has obvious mass loss between 220 ℃ and 450 ℃, but the mass loss is small (about 12%), which is mainly due to the slow decomposition of GO. The mass loss at 450 ℃ to 800 ℃ is mainly due to the collapse of COFs. However, as can be seen from the figure, the trend of the change of the mass of the GO/COFs composite material is slightly gentler than that of the COFs, which further illustrates that the mass loss of the COFs in the composite material formed by GO and COFs is reduced, and the successful preparation of GO/COFs and the good thermal stability of GO/COFs are proved.

FIG. 3b is a nitrogen adsorption analytic graph of GO/COFs composite material, and as can be seen from the graph, GO/COFs and COFs have similar isotherms, but have higher nitrogen absorption capacity under higher relative pressure, which indicates that extra macropores exist in GO/COFs, and the specific surface area of GO/COFs is 236.04 m²Per g, total pore volume 0.41 cm³G, between GO and COFs, and the average pore diameter is 5.46 nm. The prepared GO/COFs have larger aperture, and are beneficial to the adsorption and diffusion of pollutants in mesopores.

Adsorption of organic pollutants

Putting the adsorbent GO/COFs composite material into an organic pollutant aqueous solution, wherein the organic pollutants are naphthalene, 1-naphthylamine and 1-naphthol, the concentration of the naphthalene in the organic pollutants is 2 to 50 mg/L, and the concentration of the 1-naphthylamine and the 1-naphthol is 2 to 120 mg/L. The ratio of the mass (g) of the adsorbent to the volume (L) of the aqueous organic contaminant solution was 1. The adsorption experiment is carried out in a shaking table at the temperature of 20 to 40 ℃ for 0.5 to 3 hours, and the concentration of the organic pollutants is determined by high performance liquid chromatography after the composite material is separated from the solution by centrifuging through a centrifugal machine.

The adsorption process is generally explained by Langmuir and Freundlich isotherms. Langmuir assumes that the surface energy of the adsorbent is uniform, each adsorption site has the same affinity for an adsorbate molecule, each adsorption site can only accommodate one adsorbate molecule, no lateral interaction exists between adsorbed molecules, and the adsorption process is monomolecular adsorption. Freundlich assumes that the surface energy of the adsorbent is not uniform, the adsorption sites with higher energy are more easily occupied by adsorbate molecules, and two or even more adsorption sites can jointly adsorb one adsorbate molecule, which is adsorption of a multi-molecular layer. Table 1 shows fitting parameters of adsorption isotherms of organic pollutants on GO, COFs and GO/COFs. FIG. 4 is a graph of adsorption isotherms of naphthalene on GO, COFs and GO/COFs. As can be seen from FIG. 4 and Table 1, naphthalene is more compatible with Langmuir isotherm and mainly adsorbed by a monolayer, and naphthalene adsorbs 112, 182 and 211mg/g at the maximum adsorption amounts of GO, COFs and GO/COFs, respectively. FIGS. 5 (a) and (b) are graphs of adsorption isotherms of 1-naphthol and 1-naphthylamine, respectively. As can be seen from FIG. 5 and Table 1, 1-naphthylamine and 1-naphthol more conform to the Freundlich adsorption isotherm, and the adsorption process is mainly multi-molecular-layer adsorption. The maximum adsorption amounts of 1-naphthylamine at GO, COFs and GO/COFs are respectively 96.6, 63.1 and 110 mg/g, and the maximum adsorption amounts of 1-naphthol at GO, COFs and GO/COFs are respectively 87.5, 71.9 and 98.2 mg/g.

In the evaluation of the performance of the adsorbent, the recycling of the adsorbent is an important parameter. After adsorbing organic pollutants, the GO/COFs composite material is desorbed by ultrasonic in ethanol. Five cycles of adsorption-desorption were performed to investigate the sorbent recoverability. FIG. 6 is a graph of the recycling of the GO/COFs composite material to naphthalene, 1-naphthylamine, 1-naphthol. From the figure, it can be seen that after 5 times of cycle experiments, the organic pollutant adsorption amount of GO/COFs is still more than 88% compared with the original adsorbent. Experimental results show that the GO/COFs have good reusability and can be used as a potential adsorbent for removing organic pollutants in wastewater.

In conclusion, the GO/COFs composite material is prepared at room temperature through in-situ growth, can be used for adsorbing organic pollutants, and has good adsorption performance and good reutilization performance on organic pollutants such as naphthalene, 1-naphthylamine and 1-naphthol.

Drawings

FIG. 1 is a Transmission Electron Microscope (TEM) image of GO (a) and COFs (b); scanning Electron Microscope (SEM) images (c) of COFs; TEM (d), high Resolution Transmission Electron Microscopy (HRTEM) (e) and elemental distribution maps (f) for GO/COFs.

FIG. 2 shows XRD pattern (a) and infrared spectrum (b) of GO/COFs.

FIG. 3 is a thermogravimetric graph (a) and a nitrogen adsorption analytic graph (b) of GO/COFs.

FIG. 4 is an adsorption isotherm diagram of naphthalene at GO, COFs and GO/COFs, with the solid line being the Langmuir isotherm and the dotted line being the Freundlich isotherm.

FIG. 5 is the adsorption isotherms of 1-naphthol (a) and 1-naphthylamine (b) at GO, COFs and GO/COFs, with the solid line being the Langmuir isotherm and the dotted line being the Freundlich isotherm.

FIG. 6 is a graph of recycling organic pollutants naphthalene, 1-naphthylamine and 1-naphthol from GO/COFs composite material.

Detailed Description

The following will further explain the preparation of the GO/COFs composite material and the application thereof in organic pollutant adsorption by specific embodiments.

Example 1

(1) Preparation of GO/COFs composite material

First, GO was synthesized according to Hummers method. 0.0426g of 1,3, 5-tris (4-aminophenyl) benzene and 0.4 mL of acetic acid (17 mol) were dissolved in 8 mL of acetonitrile, and then 6.5 mL of 5 mg/mL GO was added and stirred for 30 min to obtain a uniform dispersion. The dispersion was then transferred to a 50ml centrifuge tube, and 0.0224g of 2, 5-divinyl-1, 4-benzenedicarboxaldehyde dissolved in 2ml of acetonitrile was added thereto. Then shaken vigorously in a vortex mixer and allowed to stand at room temperature for 72 h. The collected green precipitate is washed with tetrahydrofuran and ethanol and dried, and the yield reaches over 90 percent.

(2) Organic pollutant adsorption of GO/COFs composite material

Respectively putting a series of the prepared GO/COFs composite material 4 mg into a 10 mL centrifuge tube, and adding 8 mL of organic pollutant aqueous solutions with different concentrations (the concentration of naphthalene is 2,5, 10, 20, 30, 40 and 50 mg/L in sequence; the concentration of 1-naphthylamine and 1-naphthol is 2,5, 10, 20, 40, 60, 80, 100 and 120 mg/L in sequence); the adsorption experiments were carried out in a shaker at 25 ℃ for 3 h at 200 rpm. After the adsorption was completed, separation was performed by centrifugation and the supernatant was collected. High performance liquid chromatography was used to determine the concentration of organic contaminants in the supernatant. The maximum adsorption amount of naphthalene finally obtained is 211mg/g, the maximum adsorption amount of 1-naphthylamine is 110 mg/g, and the maximum adsorption amount of 1-naphthol is 98.2 mg/g.

Example 2

(1) Preparation of GO/COFs composite material

0.0426g of 1,3, 5-tris (4-aminophenyl) benzene and 0.8 mL of acetic acid (17 mol) were dissolved in 8 mL of acetonitrile, and then 13 mL of 5 mg/mL GO was added and stirred for 10 min to obtain a uniform dispersion. The dispersion was then transferred to a 50ml centrifuge tube, to which 0.0224g of 2, 5-divinyl-1, 4-benzenedicarboxaldehyde dissolved in 2ml of acetonitrile was added. Then shaken vigorously in a vortex mixer and allowed to stand at room temperature for 6 h. The collected green precipitate was washed with acetone and ethanol and dried, yielding over 90%.

(2) Organic pollutant adsorption of GO/COFs composite material

Respectively putting a series of 4 mg of the prepared GO/COFs composite material into 10 mL of a centrifuge tube, and adding 8 mL of organic pollutant aqueous solutions with different concentrations (the concentration of naphthalene is sequentially 2,5, 10, 20, 30, 40, 50 mg/L; the concentration of 1-naphthylamine and 1-naphthol is sequentially 2,5, 10, 20, 40, 60, 80, 100, 120 mg/L); the adsorption experiment was carried out in a shaker at 25 ℃ for 3 h and at 200 rpm. After the adsorption was completed, separation was performed by centrifugation and the supernatant was collected. The concentration of organic contaminants in the supernatant was determined using high performance liquid chromatography. The maximum adsorption capacity of the finally obtained naphthalene is 210mg/g, the maximum adsorption capacity of the 1-naphthylamine is 108 mg/g, and the maximum adsorption capacity of the 1-naphthol is 96 mg/g.

Example 3

(1) Preparation of GO/COFs composite material

0.0213 g of 1,3, 5-tris (4-aminophenyl) benzene and 0.2 mL of acetic acid (17 mol) were dissolved in 8 mL of acetonitrile, and 13 mL of 5 mg/mL GO was added and stirred for 30 min to obtain a uniform dispersion. The dispersion was then transferred to a 50ml centrifuge tube, to which 0.0112 g of 2, 5-divinyl-1, 4-benzenedicarboxaldehyde dissolved in 2ml of acetonitrile was added. Then shaken vigorously in a vortex mixer and allowed to stand at room temperature for 24 h. The collected green precipitate was washed with tetrahydrofuran and ethanol and dried, yielding over 90%.

(2) Respectively putting a series of 4 mg of the GO/COFs composite material prepared above into 10 mL centrifuge tubes, and adding 8 mL of organic pollutant aqueous solutions with different concentrations (the concentration of naphthalene is sequentially 2,5, 10, 20, 30, 40, 50 mg/L; and the concentration of 1-naphthylamine and 1-naphthol is 2,5, 10, 20, 40, 60, 80, 100, 120 mg/L); the adsorption experiments were carried out in a shaker at 20 ℃ for 1 h and at 100 rpm. After the adsorption was completed, separation was performed by centrifugation and the supernatant was collected. High performance liquid chromatography was used to determine the concentration of organic contaminants in the supernatant. The maximum adsorption capacity of the finally obtained naphthalene is 211mg/g, the maximum adsorption capacity of the 1-naphthylamine is 109 mg/g, and the maximum adsorption capacity of the 1-naphthol is 98 mg/g.

Claims

1. A GO/COFs composite material preparation method comprises the steps of mixing 1,3, 5-tris (4-aminophenyl) benzene and acetic acid, adding an acetonitrile solution, carrying out ultrasonic treatment to dissolve a solid, adding a graphene oxide suspension, and stirring for 5-30 min to obtain a uniform dispersion liquid; and then adding an acetonitrile solution of 2, 5-divinyl-1, 4-benzene dicarboxaldehyde into the uniform dispersion liquid, violently shaking in a vortex mixer to uniformly mix the mixture, standing at room temperature for 2 to 72 hours, washing an obtained green precipitate crude product with tetrahydrofuran and ethanol, and drying to obtain the GO/COFs composite material.

2. The method for preparing GO/COFs composite material according to claim 1, wherein: the molar ratio of the 1,3, 5-tris (4-aminophenyl) benzene to acetic acid is 1.

3. The method for preparing GO/COFs composite material according to claim 1, wherein: the molar ratio of the 1,3, 5-tris (4-aminophenyl) benzene to the 2, 5-divinyl-1, 4-benzenedicarboxaldehyde is 2.

4. The method for preparing GO/COFs composite material according to claim 1, wherein: the mass ratio of the total mass of the 1,3, 5-tri (4-aminophenyl) benzene and the 2, 5-divinyl-1, 4-benzene dicarbaldehyde to the graphene oxide is 1.

5. The GO/COFs composite material prepared by the method of claim 1, being applied to adsorption of organic pollutants.

6. The use of GO/COFs composites according to claim 5 for the adsorption of organic pollutants, wherein: adding the GO/COFs composite material prepared in the above into an organic pollutant aqueous solution, wherein the organic pollutants are naphthalene, 1-naphthylamine and 1-naphthol, and carrying out an adsorption reaction in a shaking table at a rotation speed of 100-200 revolutions for 0.5-3 hours at a temperature of 20-40 ℃.

7. The use of GO/COFs composites according to claim 6 for the adsorption of organic pollutants, wherein: the concentration of the organic pollutant naphthalene is 2 to 50 mg/L, and the concentration of the 1-naphthylamine and the concentration of the 1-naphthol are 2 to 120 mg/L.

8. The use of GO/COFs composites according to claim 6 for the adsorption of organic pollutants, wherein: the mass-volume ratio of the GO/COFs composite material to the organic pollutant aqueous solution is 0.5g/L.