CN103480333A - Compound grapheme absorption agent, method for preparing compound grapheme absorption agent and application of compound grapheme absorption agent - Google Patents

Abstract

The invention discloses a composite graphene adsorbent, which comprises graphene, nanometer zero-valent iron and cetyltrimethylammonium bromide. The present invention also discloses a preparation method of the above-mentioned composite graphene adsorbent, which includes the following steps: (1) dispersing graphene oxide in water, and obtaining a graphene oxide suspension through ultrasonic dispersion; (2) in step (1) ) Add nanometer zero-valent iron and hexadecyltrimethylammonium bromide to the obtained graphene oxide suspension, stir fully, and obtain a reaction solution after complete reaction; (3) add the reaction solution obtained in step (2) A reducing agent, after fully reacting, a black flocculent precipitate is obtained; (4) the black flocculent precipitate obtained after step (3) is suction filtered, washed and dried to obtain a composite graphene adsorbent. The composite graphene adsorbent of the present invention is highly efficient, green, economical and environmentally friendly, has a simple preparation method, easy controllable conditions, and is suitable for large-scale production.

Description

A kind of composite graphene adsorbent and its preparation method and application

technical field

The invention relates to the field of organic pollutant adsorbents, in particular to a composite graphene adsorbent and its preparation method and application.

Background technique

Due to the rapid development of industry and the continuous improvement of people's living standards, the proportion of organic pollutants in polluted water bodies is increasing. As a harmful and refractory organic pollutant, p-nitrochlorobenzene, It has been widely concerned by people for a long time. It is widely used in the production process of pesticides, medicines, dyes and rubber additives, and enters into various water bodies with the discharge of industrial wastewater. As a result, it can be detected in some major water bodies in my country. The presence of nitrochlorobenzene. In addition to causing methemoglobinemia in humans and other mammals, it is a mutagen and carcinogen and is difficult to degrade in the environment. Therefore, it is of great significance to study the removal of p-nitrochlorobenzene in water to protect human health and prevent environmental damage.

At present, the treatment methods of organic pollutants in aqueous solution that have been developed and applied mainly include physical methods, chemical reduction methods, advanced oxidation methods, and biological methods, among which more than 90% use chemical methods, and the main chemical methods include: chemical precipitation, membrane, etc. Separation method, ion exchange method, electrolysis method, electrodialysis method, activated carbon adsorption method, etc. Among these methods, the adsorption method is a method for removing organic pollutants in aqueous solution with low equipment investment, simple operation, high efficiency and easy to be widely used. The key to improving the adsorption method is to develop new types of adsorption that are more efficient, environmentally friendly and inexpensive. Material.

Currently, a large number of adsorbent materials have been reported to remove organic pollutants in water bodies, such as activated carbon, fly ash, biomass adsorbents, etc. Due to their large specific surface area, nanomaterials are regarded as a more efficient adsorption material, which is beneficial to the removal of organic pollutants in aqueous solutions. For example, carbon nanotubes have been proved to be a very effective new adsorbent for organic pollutants, and its efficiency is 5-7 times higher than that of ordinary activated carbon adsorbents. However, the disadvantages of high cost, easy to produce secondary pollution and difficult to remove limit the use of carbon nanotubes. In response to this problem, the development of more efficient, economical and non-toxic nano-adsorbents has become the focus of attention.

Since graphene was first developed, due to its excellent physical and chemical properties, such as large specific surface area, excellent mechanical strength, high electrical conductivity and thermal conductivity, etc., it has been widely used in chemical power sources, optoelectronic devices and heterogeneous catalysis. has received widespread attention. However, graphene materials have fewer applications in the environment. Studies have shown that graphene can remove pollutants such as organic pollutants, but the agglomeration of graphene not only reduces the specific surface area of graphene, but also is not conducive to dispersion in solution, which limits its ability to remove pollutants in aqueous solution. Remove the app.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, one of the purposes of the present invention is to provide a highly efficient, green, economical and environmentally friendly composite graphene adsorbent.

The second object of the present invention is to provide a preparation method of the above-mentioned composite graphene adsorbent, which has a simple process, easy controllable conditions, and is suitable for large-scale production.

The third object of the present invention is to provide the application of the above-mentioned composite graphene adsorbent.

The object of the present invention is achieved through the following technical solutions:

A preparation method of composite graphene adsorbent, comprising the following steps:

(1) Disperse graphene oxide in water and obtain graphene oxide suspension by ultrasonic dispersion;

(2) Add nano-zero-valent iron and cetyltrimethylammonium bromide to the graphene oxide suspension obtained in step (1); wherein, nano-zero-valent iron, graphene oxide and cetyltrimethylammonium The mass ratio of ammonium bromide is 1:2:(7-9), fully stirred, and the reaction solution is obtained after complete reaction;

(3) Heat the reaction solution obtained in step (2) to 80°C to 85°C, add a reducing agent, and obtain a black flocculent precipitate after sufficient reaction; the reducing agent is at least one of sodium borohydride and potassium borohydride ; The quality of the reducing agent is 9 to 11 times that of graphene oxide;

(4) Suction filter, wash and dry the black flocculent precipitate obtained in step (3) to obtain a composite graphene adsorbent.

The time for the ultrasonic dispersion is 30 minutes to 60 minutes.

The concentration of the graphene oxide suspension is 4 mg/mL˜6 mg/mL.

The preparation method of described nanometer zero valent iron is as follows:

Under the condition of nitrogen protection and mechanical stirring, the potassium borohydride solution was added dropwise to the FeSO ₄ solution, and the stirring was continued. After the reaction was complete, it was left to stand, and then it was vacuum filtered, washed, and vacuum dried to constant weight to obtain nanometer zero. Valence iron.

After the complete reaction in step (2), the reaction solution is obtained, specifically:

React at 50° C. to 55° C. for 3 h to 5 h to obtain a reaction solution.

The composite graphene adsorbent prepared by the above preparation method comprises graphene, nanometer zero-valent iron and cationic surfactant cetyltrimethylammonium bromide.

The nanometer zero-valent iron is inserted into the edge or surface layer of the layered graphene through chemical bonding.

The nanometer zero-valent iron is embedded in the edge or surface layer of the layered graphene through chemical bonding.

The application of the above-mentioned composite graphene adsorbent is used to remove p-nitrochlorobenzene in aqueous solution.

Described removal of p-nitrochlorobenzene in aqueous solution, concrete process is as follows:

Add 1g to 2g of composite graphene adsorbent per liter of aqueous solution; during the adsorption process, control the temperature of the aqueous solution at 20°C to 50°C, fully absorb and oscillate until the reaction is complete, and use a filter membrane to filter the remaining liquid after adsorption , complete the removal of p-nitrochlorobenzene in aqueous solution.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention makes full use of the unique physical and chemical properties of graphene and nano-zero-valent iron, and greatly reduces the agglomeration of composite graphene through cetyltrimethylammonium bromide modification, significantly improving the The specific surface area of composite graphene improves its dispersibility and hydrophilicity in solution, thereby improving its adsorption performance for organic pollutants in water;

(2) No by-products polluting the environment are produced during the preparation process of the present invention, and only conventional surfactants are used, the raw materials are simple and easy to obtain, and the preparation cost is low;

(3) The preparation process of the present invention is simple, the conditions are easy to control, and is suitable for continuous large-scale batch production; and the planar structure and essential characteristics of graphene will not be damaged during the treatment process;

(4) When the composite graphene adsorbent prepared by the present invention is used to remove p-nitrochlorobenzene in an aqueous solution, it can be directly added to an aqueous solution containing p-nitrochlorobenzene. The cost of the entire treatment process is relatively low, and the operating conditions are relatively simple And easy to implement.

Description of drawings

Fig. 1 is the scanning electron micrograph of the graphene that embodiment 1 of the present invention prepares.

FIG. 2 is a scanning electron micrograph of nanometer zero-valent iron prepared in Example 1 of the present invention.

3 is a scanning electron micrograph of the composite graphene adsorbent prepared in Example 1 of the present invention.

4 is a schematic diagram of Fourier transform infrared comparison between graphene and the composite graphene adsorbent prepared in Example 1 of the present invention.

Fig. 5 is the thermogravimetric curve of graphene and the composite graphene adsorbent prepared by Example 1 of the present invention.

Fig. 6 is a schematic diagram of comparison of the removal rates of organic pollutant p-nitrochlorobenzene at different pH values between graphene and the composite graphene adsorbent prepared in Example 1 of the present invention.

Fig. 7 is a schematic diagram of comparing the adsorption capacities of graphene and the composite graphene adsorbent prepared in Example 1 of the present invention for the organic pollutant p-nitrochlorobenzene at different treatment times.

Fig. 8 is a schematic diagram showing the comparison of adsorption isotherms of organic pollutant p-nitrochlorobenzene between graphene and the composite graphene adsorbent prepared in Example 1 of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1

The preparation method of the composite graphene adsorbent of the present embodiment may further comprise the steps:

(1) Disperse graphene oxide in water, and obtain a graphene oxide suspension with a concentration of 4 mg/mL after ultrasonic dispersion for 30 minutes;

The graphene oxide of the present embodiment is synthesized by the modified Hummers method, and the specific steps are as follows: 10 g of graphite and 5 g of sodium nitrate are slowly added to a flask containing 230 ml of concentrated sulfuric acid, and stirred in an ice-water mixture. After 30 min, slowly add 30 g Potassium permanganate, during the stirring process, control the reaction temperature to always be less than 15°C and keep it for 90 minutes; transfer the reaction system to a constant temperature water bath at 35°C, keep the reaction temperature at 35°C, and stir for 30 minutes; add 460mL of Deionized water, the reaction temperature is controlled at 80°C to 95°C, and the stirring time is 30min; then add 100mL of 30% hydrogen peroxide solution, filter it while it is hot after the solution turns bright yellow, and use 500mL of 5% hydrochloric acid The solution was washed three times with 1400mL deionized water until the solution was free of sulfate ions (detected with barium chloride solution). The obtained sample was dried in a vacuum freeze dryer at 50°C for 48 hours to constant weight to obtain graphene oxide, the microstructure of which is shown in Figure 1.

(2) Add nano-zero-valent iron and cetyltrimethylammonium bromide to the graphene oxide suspension obtained in step (1); wherein, nano-zero-valent iron, graphene oxide and cetyltrimethylammonium The mass ratio of ammonium bromide is 1:2:7, fully stirred, and reacted at 55°C for 3h, and obtained a reaction solution after complete reaction;

The synthetic method of the nanometer zero-valent iron of the present embodiment is as follows:

Dissolve 11.12g FeSO ₄ ·7H ₂ O in 200mL ethanol aqueous solution (ethanol: water = 3:7) at room temperature, and in a 1000mL three-necked flask, under nitrogen protection and mechanical stirring, 200mL concentration is 0.12mol/L Potassium borohydride solution was quickly added dropwise to the FeSO ₄ solution, and the stirring reaction was continued for 30 min. After standing still for 5 minutes, it was vacuum-filtered, washed several times with ultrapure water and absolute ethanol, and vacuum-dried to constant weight to obtain nanometer zero-valent iron. The microstructure is shown in Figure 2.

(3) Heating the reaction solution obtained in step (2) to 80°C, adding a reducing agent sodium borohydride, and obtaining a black flocculent precipitate after sufficient reaction; the mass of the reducing agent is 10 times the mass of graphene oxide;

(4) Suction filter, wash and dry the black flocculent precipitate obtained in step (3) to obtain a composite graphene adsorbent.

The microstructure of the composite graphene adsorbent that the present embodiment obtains is as shown in Figure 3, compared with the graphene of a large amount of agglomeration in Figure 1, the graphene in Figure 3 becomes thinner, presents lamellar structure, And the interlamellar spacing increases, which may be attributed to the introduction of cetyltrimethylammonium bromide, and it can be clearly seen from Figure 3 that the nano-zero-valent iron particles are uniformly attached to the graphene surface or in the lamellae .

Figure 4 is a schematic diagram of Fourier transform infrared comparison between graphene and the composite graphene adsorbent prepared in this embodiment. The composite graphene adsorbent prepared in this example has methylene and methyl CH stretching vibrations in the bands of 2918cm ^-1 and 2849cm ^-1 , which proves that the composite graphene adsorbent contains hexadecyltrimethyl bromide Ammonium; the composite graphene adsorbent has carbonyl stretching vibration in the band of 1643cm ^- 1, and the stretching vibration of intermolecular OH bonds in the band of 3201cm ^- 1, which proves that the composite graphene adsorbent contains nanometer zero-valent iron. The functional groups on the surface of graphene are mainly distributed on the edge or surface layer, and the functional groups in the nano-zero-valent iron combine with the functional groups on the graphene surface, so that the nano-zero-valent iron is inserted or embedded in the edge or surface layer of the layered graphene through chemical bonds.

Fig. 5 is the thermogravimetric curve of graphene and the composite graphene adsorbent prepared in Example 1. As can be seen from the figure, the composite graphene adsorbent prepared in this embodiment contains about 56% graphene, about 10% nanometer zero-valent iron, and about 14% cationic surfactant hexadecyltrimethyl by mass percentage. Ammonium bromide and about 20% impurities.

Example 2

The preparation method of the composite graphene adsorbent of the present embodiment may further comprise the steps:

(1) Disperse graphene oxide in water, and obtain a graphene oxide suspension with a concentration of 6 mg/mL after ultrasonic dispersion for 60 minutes;

(2) Add nano-zero-valent iron and cetyltrimethylammonium bromide to the graphene oxide suspension obtained in step (1); wherein, nano-zero-valent iron, graphene oxide and cetyltrimethylammonium The mass ratio of ammonium bromide is 1:2:9, fully stirred, and reacted for 5h at 50°C, and obtained a reaction solution after complete reaction;

(3) Heating the reaction solution obtained in step (2) to 85°C, adding a reducing agent potassium borohydride, and obtaining a black flocculent precipitate after sufficient reaction; the mass of the reducing agent is 9 times the mass of graphene oxide;

(4) Suction filter, wash and dry the black flocculent precipitate obtained after step (3) to obtain a composite graphene adsorbent.

The microstructure and infrared spectrum analysis results of the composite graphene adsorbent prepared in this example are similar to Example 1.

Example 3

The preparation method of the composite graphene adsorbent of the present embodiment may further comprise the steps:

(1) Disperse graphene oxide in water, and obtain a graphene oxide suspension with a concentration of 5 mg/mL after ultrasonic dispersion for 40 minutes;

(2) Add nano-zero-valent iron and cetyltrimethylammonium bromide to the graphene oxide suspension obtained in step (1); wherein, nano-zero-valent iron, graphene oxide and cetyltrimethylammonium The mass ratio of ammonium bromide is 1: 2: 8, fully stirred, and reacted for 4 hours at 52 ° C, and obtained a reaction solution after complete reaction;

(3) Heating the reaction solution obtained in step (2) to 82°C, adding a reducing agent sodium borohydride, and obtaining a black flocculent precipitate after fully reacting; the total mass of the reducing agent is 11 times the mass of graphene oxide;

(4) Suction filter, wash and dry the black flocculent precipitate obtained after step (3) to obtain a composite graphene adsorbent.

The microstructure and infrared spectrum analysis results of the composite graphene adsorbent prepared in this example are similar to Example 1.

Application example

Test 1:

(1) The composite graphene adsorbent in Example 1 was divided into 6 groups, and then added to the aqueous solution containing p-nitrochlorobenzene with an initial concentration of p-nitrochlorobenzene of 200ppm, and the dosage of the adsorbent was 2mg/mL ;

(2) Perform oscillation reaction on the above-mentioned groups of aqueous solutions. The pH values of each group of aqueous solutions are 2, 4, 6, 8, 10 and 12 respectively. The reaction temperature of each group of aqueous solutions is 25°C. The reaction time is 120min;

(3) Use a 0.45 μm filter membrane to filter each group of aqueous solutions after the shaking reaction to complete the removal of p-nitrochlorobenzene in the aqueous solution.

Determination of the residual amount of organic pollutant p-nitrochlorobenzene in each group of aqueous solution samples, the results are shown in Figure 6. As can be seen from Figure 6, the initial pH value of the solution has no great influence on the removal of p-nitrochlorobenzene. With the graphene prepared in Example 1 (without using surfactant to modify) as a comparison sample, the operation steps during application are the same as the above-mentioned application steps, and the removal rate effect of its organic pollutant p-nitrochlorobenzene is shown in Figure 6 As can be seen from Figure 6, its removal efficiency is obviously lower than that of the composite graphene adsorbent.

test 2

Utilize the composite graphene adsorbent obtained in embodiment 1 to remove the p-nitrochlorobenzene in the aqueous solution, and concrete steps comprise:

(1) The above composite graphene adsorbents were divided into 10 groups, and then added to the aqueous solution containing p-nitrochlorobenzene with an initial concentration of p-nitrochlorobenzene of 200ppm, and the dosage of the adsorbent was 2mg/mL;

(2) Perform oscillation reaction on the above-mentioned groups of aqueous solutions. The temperature of each group of aqueous solutions is 25°C, the rotation speed of the oscillation reaction is 150rpm, and the oscillation reaction time is 0.1h, 0.2h, 0.5h, 1h, 1.5h, and 2h. , 4h, 6h, 12h and 24h;

(3) Use a 0.45m filter membrane to filter each group of aqueous solutions after the shaking reaction to complete the removal of p-nitrochlorobenzene in the aqueous solution.

Determination of the residual amount of organic pollutant p-nitrochlorobenzene in each group of aqueous solution samples, the results are shown in Figure 7. It can be seen from Figure 7 that the adsorption reaction reaches equilibrium after 2 h, then rises slowly, and finally reaches saturated adsorption. Therefore, in the actual application process, the contact time of the adsorption reaction should generally not be less than 2h. Also use the graphene prepared in Example 1 (modified without surfactant) as a comparison sample, the operation steps during application are the same as the above-mentioned application steps, and the removal rate effect of its organic pollutant p-nitrochlorobenzene is shown in the figure As shown in Figure 7, it can be seen from Figure 7 that the adsorption rate of the composite graphene adsorbent is significantly higher than that of graphene.

test 3

Utilize the composite graphene adsorbent obtained in embodiment 1 to remove the p-nitrochlorobenzene in the aqueous solution, and concrete steps comprise:

(1) Divide the above-mentioned composite graphene adsorbents into 5 groups and add them to the aqueous solutions containing p-nitrochlorobenzene with initial concentrations of 60ppm, 120ppm, 180ppm, 240ppm and 300ppm respectively. The amount of adsorbent 1 mg/mL;

(2) Perform oscillation reaction on the above-mentioned groups of aqueous solutions. The temperature of each group of aqueous solutions is 20°C, 35°C and 50°C respectively, the oscillation speed is 150rpm, and the reaction time is 120min;

(3) Use a 0.45 μm filter membrane to filter each group of aqueous solutions after the shaking reaction to complete the removal of p-nitrochlorobenzene in the aqueous solution.

The concentration of p-nitrochlorobenzene in the aqueous solution sample before and after the determination of adsorption is shown in Figure 8. It can be seen from Figure 8 that the adsorption capacity decreases with the increase of the reaction temperature, that is, low temperature is beneficial to adsorption, and the adsorption capacity per unit mass increases with the increase of the initial concentration of p-nitrochlorobenzene. According to the obtained data of equilibrium concentration (C _e ) and equilibrium adsorption capacity (q _e ) of organic pollutant p-nitrochlorobenzene, it can be known that the adsorption reaction process conforms to the Langmuir adsorption isotherm model. The results in Figure 8 show that the composite graphene adsorbent has a maximum adsorption capacity of 105 mg/g for p-nitrochlorobenzene.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (10)

1. the preparation method of a compound Graphene adsorbent, is characterized in that, comprises the following steps:

(1) graphene oxide is dispersed in water, by making graphene oxide suspension after ultrasonic dispersion;

(2) add nano zero valence iron and softex kw in the graphene oxide suspension obtained in step (1), fully stir, obtain reaction solution after complete reaction; Wherein, the mass ratio of nano zero valence iron, graphene oxide and softex kw is 1: 2: (7～9);

(3) reaction solution step (2) obtained is heated to 80 ℃～85 ℃, adds reducing agent, fully after reaction, obtains the black flocculent deposit; Described reducing agent is at least one in sodium borohydride, potassium borohydride; The quality of described reducing agent is 9～11 times of graphene oxide quality;

(4) suction filtration, washing and drying are carried out in black flocculent deposit step (3) obtained, and obtain compound Graphene adsorbent.

2. the preparation method of compound Graphene adsorbent according to claim 1, is characterized in that, the time of described ultrasonic dispersion is 30min～60min.

3. the preparation method of compound Graphene adsorbent according to claim 1, is characterized in that, the concentration of described graphene oxide suspension is 4mg/mL～6mg/mL.

4. the preparation method of compound Graphene adsorbent according to claim 1, is characterized in that, the preparation method of described nano zero valence iron is as follows:

Under nitrogen protection, churned mechanically condition, solution of potassium borohydride is added drop-wise to FeSO ₄in solution, continue to stir, react completely rear standing, then through vacuum filtration, washing, vacuum drying to constant weight, obtain nano zero valence iron.

5. the preparation method of compound Graphene adsorbent according to claim 1, is characterized in that, after the described complete reaction of step (2), obtains reaction solution, is specially:

React 3h～5h under 50 ℃～55 ℃ conditions, obtain reaction solution.

6. the compound Graphene adsorbent that the described preparation method of claim 1～5 any one prepares, comprise Graphene, nano zero valence iron and cationic surfactant softex kw.

7. compound Graphene adsorbent according to claim 6, is characterized in that, described nano zero valence iron inserts edge or the top layer of stratiform Graphene by chemical b `.

8. compound Graphene adsorbent according to claim 6, is characterized in that, described nano zero valence iron is embedded in edge or the top layer of lamellar graphite alkene by chemical b `.

9. the application of compound Graphene adsorbent claimed in claim 6, is characterized in that, for removing the paranitrochlorobenzene of the aqueous solution.

10. the application of compound Graphene adsorbent according to claim 9, is characterized in that, the paranitrochlorobenzene in the described removal aqueous solution, and detailed process is as follows:

Every premium on currency solution adds the compound Graphene adsorbent of 1g～2g; In adsorption process, the temperature of controlling the aqueous solution is 20 ℃～50 ℃, fully adsorbs and vibrate to after reacting completely, and utilizes filter membrane to be filtered the remaining liquid after adsorbing, and completes the removal to paranitrochlorobenzene in the aqueous solution.

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