WO2021143275A1 - Adsorbent based on graphene oxide, and preparation method therefor and application thereof - Google Patents

Abstract

Disclosed are an adsorbent based on graphene oxide, and a preparation method therefor and an application thereof. The adsorbent provided by the present invention has a good adsorption effect on water pollutants. The method comprises: first ultrasonically dispersing graphene oxide prepared by a Hummers method into water; then adding hydrotalcite prepared by a hydrothermal synthesis method into a graphene oxide aqueous solution having good dispersity and stirring same; intercalating negatively charged graphene oxide into hydrotalcite layers by means of the electrostatic effect, and co-precipitating with hydrotalcite, standing for layering, pouring a supernatant, and drying underlying precipitates to obtain a graphene oxide-hydrotalcite composite material, so that the agglomeration phenomenon of the graphene oxide can be effectively reduced. According to the preparation method, hydrotalcite is added into the graphene oxide solution, the operation is simple, the graphene oxide-hydrotalcite composite material is prepared, and as the agglomeration phenomenon of graphene oxide in the composite material is inhibited, the adsorption performance of the composite material is better.

Description

An adsorbent based on graphene oxide and its preparation method and application Technical field

The invention relates to the field of preparation of graphene oxide composite materials, in particular to an adsorbent based on graphene oxide and a preparation method and application thereof.

Background technique

Graphene oxide Oxide, GO) is the oxidation product of graphene. It can form negatively charged flakes in water. It has a large specific surface area and contains a variety of active oxygen-containing groups, which can provide more active sites. Therefore, graphene oxide It can be used as an adsorbent to remove various pollutants in wastewater,

Hydrotalcite is also called layered double hydroxide (Layered double hydroxides, LDH), it is a naturally occurring layered clay material. The microstructure of LDH mainly includes the main layer plate and the interlayer anion. The main layer plate has a positive charge and the interlayer anion has a negative charge. Orderly assembled together, the metal type and charge density on the main layer board are adjustable, and the interlayer anions are also exchangeable.

Graphene oxide is very easy to agglomerate, reducing its adsorption effect. Studies have shown that hydrotalcite can be combined with graphene oxide to prevent the agglomeration of graphene oxide and enhance its adsorption capacity. Garcia-Gallastegui et al. (Garcia-Gallastegui A, Iruretagoyena D, Gouvea V, et al. Graphene oxide as support for layered double hydroxides: enhancing the CO2 adsorption capacity[J]. Chemistry of Materials. 2012, 24(23): 4531 -4539.) Disperse graphene oxide in water, ultrasonically treat it to obtain a graphene oxide solution with good dispersibility, then add sodium hydroxide, sodium carbonate, magnesium nitrate and aluminum nitrate in sequence, stir evenly, and finally age at 60°C 12h, the magnesium-aluminum hydrotalcite was grown in situ on graphene oxide, and the graphene oxide-magnesium-aluminum hydrotalcite composite material was prepared by the in-situ growth method. The research results show that the composite material has a good adsorption _{of CO 2} Role; Zheng et al. (Zheng YQ, Cheng B, You W, et al. 3D hierarchical graphene oxide-NiFe LDH composite with enhanced adsorption affinity to Congo red, methyl orange and Cr(VI) ions[J]. Journal of Hazardous Materials . 2019. 369: 214-225.) The graphene oxide dispersion is mixed with Ni ²⁺ , Fe ²⁺ , and urea, and the graphene oxide-nickel-iron hydrotalcite composite material is prepared by the in-situ growth method. The research results show that , The composite material has a good adsorption effect on Congo red, methyl orange and Cr ^6+.

However, the in-situ growth method requires the preparation of hydrotalcite in the presence of graphene oxide. Therefore, the graphene oxide and hydrotalcite in the prepared composite material have defects; and the concentration of graphene oxide dispersion is relatively low, usually Under the circumstances, 1g of graphene oxide needs 1L of water to disperse well, and when preparing hydrotalcite, less water is required. Normally, 1L of water can prepare 100g of hydrotalcite, so the composite material prepared by in-situ growth method is oxidized The graphene content is small, and the ratio of graphene oxide to hydrotalcite cannot be well controlled; secondly, the in-situ growth method is complicated to operate and requires many experimental conditions.

Technical solutions

The purpose of the present invention is to provide a graphene oxide-based adsorbent and a preparation method and application thereof in view of the high cost of the current graphene oxide composite material and the difficulty of removal after adsorption. The adsorbent provided by the invention is a graphene oxide-hydrotalcite composite material prepared by a co-precipitation method, and can be applied to the field of adsorbing water pollutants. The method specifically peels and disperses graphene oxide in water, adds hydrotalcite, and stirs vigorously after ultrasonic dispersion. The graphene oxide can be peeled into negatively charged flakes in water, and the main layer of hydrotalcite is positively charged, which means graphite oxide The olefin and hydrotalcite laminates can be self-assembled to prepare graphene oxide-hydrotalcite composites through electrostatic interaction.

The purpose of the present invention is achieved through the following technical solutions.

The method for preparing a graphene oxide-based adsorbent provided by the present invention includes the following steps:

(1) Add graphene oxide to water and ultrasonically treat it to obtain a uniformly dispersed graphene oxide solution;

(2) Adding hydrotalcite to the graphene oxide solution described in step (1), ultrasonically treating, and then mechanically stirring to obtain a mixed solution;

(3) The layering phenomenon occurs after the mixed solution of step (2) is allowed to stand, the graphene oxide and hydrotalcite are co-precipitated, the supernatant is removed, and the precipitate is vacuum dried and ground to obtain the graphene oxide based adsorption Agent.

Further, the concentration of the graphene oxide solution in step (1) is 1 mg/ml-4 mg/ml.

Preferably, in step (1), the concentration of the graphene oxide solution is 2 mg/ml.

Preferably, the graphene oxide in step (1) is prepared by the Hummers method.

Further, the time of the ultrasonic treatment in step (1) is 12h-48h.

Preferably, the time of the ultrasonic treatment in step (1) is 24h.

Further, the hydrotalcite in step (2) is a hydrotalcite artificially synthesized by a hydrothermal method.

Further, the hydrotalcite in step (2) is a magnesia-aluminum hydrotalcite.

Further, the mass of the hydrotalcite in step (2) is 4-19 times the mass of the graphene oxide in step (1).

Preferably, in step (2), the mass of the added hydrotalcite is 9 times the mass of graphene oxide.

Further, the time of ultrasonic treatment in step (2) is 1-4 h, and the time of mechanical stirring is 2-8 h.

Preferably, the time of the ultrasonic treatment in step (2) is 1 h.

Preferably, the mechanical stirring time in step (2) is 2h.

Further, the standing time in step (3) is 12-24h.

Preferably, the standing time in step (3) is 24h.

The present invention provides a graphene oxide-based adsorbent obtained by the above preparation method.

The application of the graphene oxide-based adsorbent provided by the present invention in adsorbing water pollutants.

Graphene oxide can be exfoliated in water to form negatively charged flakes, while the main hydrotalcite layer has a positive charge. The main layer of graphene oxide and hydrotalcite can be prepared by electrostatic interaction and self-assembly to obtain a graphene oxide-hydrotalcite composite Material.

Graphene oxide adsorbs methylene blue mainly by using its larger specific surface area. Hydrotalcite has no adsorption effect on methylene blue, and graphene oxide is very easy to agglomerate, which will reduce the adsorption effect. The adsorption effect of composite materials mainly comes from graphene oxide. After the composite material is formed, the agglomeration of graphene oxide is suppressed, so its adsorption effect is better than that of agglomerated graphene oxide.

The present invention prepares the graphene oxide-hydrotalcite composite material by the co-precipitation method. On the one hand, it can inhibit the agglomeration of graphene oxide. On the other hand, the hydrotalcite can be co-precipitated with graphene oxide, which is easily removed after adsorption and does not produce new Pollution. Therefore, the adsorption effect of the graphene oxide-hydrotalcite composite material is better than that of the agglomerated graphene oxide. The most important thing is that the graphene oxide-hydrotalcite composite material can greatly reduce the use cost of graphene oxide.

The present invention first prepares graphene oxide and hydrotalcite separately, and then peels off the layered graphene oxide and hydrotalcite through ultrasonic and stirring treatment. The graphene oxide and hydrotalcite will self-assemble together due to electrostatic action, and then co-precipitate. This method It is easy to operate, does not damage the structure of graphene oxide and hydrotalcite in the process of preparing the composite material, and can accurately control the ratio of graphene oxide to hydrotalcite in the composite material.

Beneficial effect

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

The graphene oxide-based adsorbent provided by the present invention has a graphene oxide content of only 5%-25%, but its adsorption efficiency is much higher than graphene oxide or hydrotalcite, which reduces the use cost of graphene oxide as an adsorbent The most important thing is that after the adsorption is completed, the graphene oxide-based adsorbent will naturally precipitate, without complicated operations such as centrifugation, which improves its practical application value.

Description of the drawings

Figure 1 is an infrared spectrogram of the graphene oxide-based adsorbent prepared in Example 1;

2 is a bar graph showing the removal efficiency of hydrotalcite, graphene oxide, and graphene oxide-based adsorbents for methylene blue in the examples.

Embodiments of the present invention

The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments and drawings, but the protection scope and implementation manners of the present invention are not limited thereto.

Example 1

A method for preparing a graphene oxide-based adsorbent, the specific steps are as follows:

(1) Put 1g The graphene oxide prepared by the Hummers method was added to 500 mL of deionized water and treated with ultrasound for 24 hours to obtain a uniformly dispersed graphene oxide solution;

(2) Add 4 g of the magnesium-aluminum hydrotalcite prepared by the hydrothermal synthesis method to the graphene oxide solution described in step (1), ultrasonically treat for 1 hour, and then stir with a stirring blade for 2 hours to obtain a mixed solution;

(3) Leave the mixed solution in step (2) for 24 hours. It can be observed that the graphene oxide and hydrotalcite co-precipitate, and the solution is stratified. Discard the supernatant, vacuum dry and grind the lower layer of the precipitate to obtain the result. The adsorbent based on graphene oxide.

The infrared spectrum of the graphene oxide-based adsorbent prepared in Example 1 is shown in FIG. 1.

The graphene oxide-based adsorbent prepared in Example 1 is used in the field of adsorbing water pollutants. This example is methylene blue. The specific steps are as follows:

(1) Configure 10mg/L methylene blue solution, weigh 40ml methylene blue solution into three 100ml beakers, and add 40mg hydrotalcite, graphene oxide and graphene oxide-based adsorbent to these three beakers. , Shake the three beakers in a water bath for 1 hour to study the adsorption effect of the three adsorbents on methylene blue;

(2) After the adsorption is completed, suck the supernatant with a pipette, measure the absorbance of the supernatant with an ultraviolet spectrophotometer, and calculate the removal efficiency of hydrotalcite, graphene oxide, and graphene oxide-hydrotalcite composite materials for methylene blue.

The removal efficiency of methylene blue by hydrotalcite, graphene oxide and graphene oxide-based adsorbents is shown in Figure 2. In Figure 2, LDH stands for hydrotalcite, GO stands for graphene oxide, and GO-LDH stands for graphene oxide-based adsorption. It can be seen from Figure 2 that the removal rate of methylene blue by the graphene oxide-based adsorbent is 98.02%, which is much higher than the removal rate of graphene oxide for methylene blue of 90.53% and hydrotalcite of 28.51 for methylene blue. %.

Example 2

A method for preparing a graphene oxide-based adsorbent, the specific steps are as follows:

(1) Add 1 g of graphene oxide prepared by Hummers method to 500 mL of deionized water, and ultrasonically treat for 12 hours to obtain a uniformly dispersed graphene oxide solution;

(2) Add 9 g of the magnesium-aluminum hydrotalcite prepared by the hydrothermal synthesis method to the graphene oxide solution described in step (1), ultrasonically treat it for 2 hours, and then stir with a stirring blade for 4 hours to obtain a mixed solution;

(3) The mixed solution described in step (2) is allowed to stand for 12 hours. It can be observed that the graphene oxide and hydrotalcite are co-precipitated, and the solution is stratified. The supernatant is discarded, the lower sediment is vacuum dried, and the lower sediment is ground. The adsorbent based on graphene oxide.

The graphene oxide-based adsorbent prepared in Example 2 also has a good removal effect on methylene blue, as shown in FIG. 2.

Example 3

A method for preparing a graphene oxide-based adsorbent, the specific steps are as follows:

(1) Put 1g The graphene oxide prepared by the Hummers method was added to 500 mL of deionized water, and ultrasonic treatment was performed for 48 hours to obtain a uniformly dispersed graphene oxide solution;

(2) Add 19 g of the magnesium-aluminum hydrotalcite prepared by the hydrothermal synthesis method to the graphene oxide solution described in step (1), ultrasonically treat for 4 hours, and then stir with a stirring blade for 8 hours to obtain a mixed solution;

(3) Leave the mixed solution in step (2) for 18 hours. It can be observed that the graphene oxide and hydrotalcite co-precipitate and the solution is stratified. Discard the supernatant, vacuum dry and grind the lower layer of the precipitate to obtain the result. The adsorbent based on graphene oxide.

The graphene oxide-based adsorbent prepared in Example 3 also has a good removal effect on methylene blue, as shown in FIG. 2.

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

Claims (10)

1. A method for preparing a graphene oxide-based adsorbent is characterized in that it comprises the following steps:

   (1) Add graphene oxide to water and ultrasonically process to obtain graphene oxide solution;

   (2) Adding hydrotalcite to the graphene oxide solution described in step (1), ultrasonically treating, and then mechanically stirring to obtain a mixed solution;

   (3) The layering phenomenon occurs after the mixed solution in step (2) is allowed to stand, the supernatant is removed, and the precipitate is dried and ground to obtain the graphene oxide-based adsorbent.
2. The preparation method according to claim 1, wherein the concentration of the graphene oxide solution in step (1) is 1 mg/ml-4 mg/ml.
3. The preparation method according to claim 1, wherein the time of the ultrasonic treatment in step (1) is 12h-48h.
4. The preparation method according to claim 1, wherein the hydrotalcite in step (2) is a hydrotalcite artificially synthesized by a hydrothermal method.
5. The preparation method according to claim 1, wherein the hydrotalcite in step (2) is a magnesia-aluminum hydrotalcite.
6. The preparation method according to claim 1, wherein the mass of the hydrotalcite in step (2) is 4-19 times the mass of the graphene oxide in step (1).
7. The preparation method according to claim 1, characterized in that the time of the ultrasonic treatment in step (2) is 1 to 4 hours, and the time of mechanical stirring is 2 to 8 hours.
8. The preparation method according to claim 1, wherein the standing time in step (3) is 12-24h.
9. The graphene oxide-based adsorbent obtained by the preparation method of any one of claims 1-8.
10. The use of the graphene oxide-based adsorbent of claim 9 in adsorbing water pollutants.