CN108516539B - A kind of preparation method of graphene hydrogel and its application in wastewater treatment - Google Patents

Abstract

Application the present invention provides a kind of preparation method of graphene hydrogel and its in the treatment of waste water, the preparation method include mixing silver sulfide quantum dot stoste with graphene oxide, at 100-300 DEG C heat 0.5~10h to get.Graphene oxide layer is restored using the silver sulfide quantum dot for containing abundant functional group as reducing agent and crosslinking agent and is shaped to three-dimensional porous graphene hydrogel by the present invention.Graphene hydrogel of the invention can adsorb to rapid, high volume the organic dyestuff in waste water, and processing method and device therefor are simple and convenient to operate, and have very high application value and commercial value.

Description

A kind of preparation method of graphene hydrogel and its application in wastewater treatment

technical field

The invention relates to the field of wastewater treatment containing organic dyes, in particular to a preparation method of a graphene hydrogel and its application in wastewater treatment.

Background technique

The continuous development of society has promoted the development of the chemical industry, but in the process of development, industrial wastewater is also increasing. Organic dye wastewater is one of the main harmful industrial wastewaters, mainly from the dye and dye intermediate generation industry. Organic dyes mainly refer to aromatic halides, aromatic nitro compounds, aromatic amine compounds, biphenyls and other polyphenyl ring substitutions generated after the hydrogen on the benzene ring of organic aromatic compounds is substituted by halogen, nitro, and amine groups. Compounds have high biological toxicity, and some are still "three identical" substances. How to effectively deal with organic dyes is the focus of people's research. The current main methods include solution extraction, adsorption, reverse osmosis, chemical oxidation, photocatalysis, and biodegradation.

Since graphene was reported by Novoselov et al. of the University of Manchester in 2004, its excellent electrical conductivity, thermal conductivity and mechanical properties have immediately attracted extensive attention of researchers at home and abroad. The large-scale preparation of graphene is the premise of conducting graphene application research. At present, graphene preparation methods include: micromechanical exfoliation, epitaxial growth, chemical vapor deposition, supercritical fluid exfoliation, and chemical redox methods. Among them, chemical redox method is currently the most widely used method for large-scale preparation of graphene. The method mainly includes two parts: (1) intercalation and oxidation of graphite; (2) exfoliation and reduction of graphite oxide.

Hydrogel is a kind of functional polymer material with a three-dimensional network structure that integrates water absorption, water retention, and sustained release. It is widely used in medicine and bioengineering due to its good biocompatibility. Combining hydrogels with two-dimensional graphene nanosheets can prepare graphene-based hydrogels with excellent electrochemical and mechanical properties, expanding their applications in various fields. Among them, the use of graphene hydrogels as adsorbents to remove pollutants in water is a trend of research due to its large specific surface area and porous structure.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a kind of preparation method of graphene hydrogel, and this preparation method comprises the steps:

The silver sulfide quantum dot stock solution is mixed with graphene oxide, and heated at 100-300° C. for 0.5-10 hours to obtain the solution.

In a preferred embodiment of the present invention, the heating temperature is 120-180° C., and the heating time is 0.5-2 h. Within this temperature time, it can be ensured that the finally obtained stone hydrogel has a three-dimensional structure and high absorption efficiency.

Among them, in the present invention, the mixed system can be transferred to a reaction kettle, and placed in an oven at the above temperature for reaction.

In a preferred embodiment of the present invention, the volume-to-mass ratio of the silver sulfide quantum dot stock solution to graphene oxide is 1mL:(0.1-10)mg; preferably 1mL:(0.5-3.5)mg, more preferably 1mL: 1mg.

In a preferred embodiment of the present invention, the silver sulfide quantum dot stock solution can be mixed with graphene oxide using ultrasound. The power of the ultrasound is preferably 50-500W, and the time is preferably 0.1-10h; more preferably, the power is 100-220W, and the time is 0.3-1.8h; more preferably, the power is 150W, and the time is 0.5h.

In a preferred embodiment of the present invention, the preparation method further includes diluting the mixed solution before heating, and the dilution ratio is 0-20 times.

In the present invention, a method commonly used in the art can be used to obtain the sulfided quantum dot stock solution. In a preferred embodiment of the present invention, the preparation method of the sulfided quantum dot stock solution is preferably as follows:

Ag inorganic salt and dodecanethiol are prepared by hydrothermal synthesis method under alkaline conditions to prepare oil-soluble silver sulfide quantum dots, and then the surface functional groups of the oil-soluble silver sulfide quantum dots are modified with thioglycolic acid. , to obtain the silver sulfide quantum dot stock solution.

Among them, the temperature of the hydrothermal synthesis method is preferably 180 to 200°C.

The preparation method of the sulfided quantum dot stock solution is preferably the preparation method disclosed in Chinese patent application CN106753344A.

The graphene hydrogel prepared by the above preparation method has a three-dimensional porous loose structure, wherein the graphene stacks form a basic skeleton, the silver sulfide quantum dots are evenly distributed on the surface as the connection points between the lamellae, and the silver sulfide also acts as a reducing agent. Graphene oxide is reduced to graphene.

Another object of the present invention is to provide the graphene hydrogel prepared by the above preparation method.

Using the graphene hydrogel of the present invention can effectively treat wastewater, especially can effectively adsorb organic dyes in wastewater.

Another object of the present invention is to provide the above-mentioned preparation method or the application of the graphene hydrogel prepared by the above-mentioned preparation method in the treatment of wastewater containing organic dyes.

The application preferably specifically includes the following steps:

The graphene hydrogel is adsorbed with wastewater containing organic dyes; the rotation speed of the adsorption is 50-500r/min, and the adsorption time is 0.1-10h. Preferably, the rotation speed of adsorption is 150-300r/min, and the adsorption time is 0.5-3h. More preferably, the rotation speed of adsorption is 200r/min, and the adsorption time is 1h. The above adsorption is preferably oscillation adsorption.

The temperature of the adsorption is 0 to 45°C, preferably 20 to 30°C.

Wherein, the mass volume ratio of the graphene hydrogel to the organic dye-containing wastewater is preferably (20-50) mg:100 mL, more preferably (30-40) mg:100 mL.

Wherein, the organic dye is preferably methyl orange, methylene blue or rhodamine B. The concentration of the organic dye is preferably less than or equal to 1000 mg/L.

Compared with the prior art, the beneficial effects of the present invention:

1. The present invention uses silver sulfide quantum dots rich in functional groups as reducing agents and cross-linking agents at a specific temperature and time to reduce and shape the graphene oxide sheet into a three-dimensional porous graphene hydrogel by a hydrothermal method. , The graphite hydrogel has a large specific surface area. It has a good adsorption performance for organic dyes when it is used to treat wastewater. It has a fast adsorption rate (the adsorption can be completed within half an hour) and a large adsorption capacity (up to 220mg/ g), the advantage of high recycling rate (at least 4 to 5 times can be repeated, and the adsorption capacity of graphene hydrogel is not significantly weakened after 4 to 5 repetitions).

2. The method of the present invention is simple, easy to operate, and has good reproducibility, and is a means to quickly obtain graphene hydrogels. The obtained graphene hydrogels have ideal effects in treating wastewater containing organic dyes, and organic dye wastewater is Industrial wastewater and domestic wastewater account for a large proportion, and the technical solution of the present invention can be widely used in the treatment of organic dye wastewater.

Description of drawings

Fig. 1 is the isotherm adsorption curves of graphene hydrogels prepared in Examples 3-5 of the present invention.

FIG. 2 is a straight line diagram of fitting the Langmuir adsorption model of the graphene hydrogels prepared in Examples 3 to 5 of the present invention.

Detailed ways

The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available commodities.

Example 1

The present embodiment provides a silver sulfide quantum dot, and its preparation method is as follows:

(1) Dissolve 5mmol AgNO ₃ in 20ml deionized water to form a colorless and transparent solution, then under vigorous stirring, add concentrated ammonia water dropwise until the resulting brown precipitate completely disappears.

(2) This solution was transferred to the reaction kettle, 3 ml of dodecanethiol was added as the oil phase, and the solution was placed in an oven at 200° C. for 3 hours.

(3) Collect the precipitate and discard the supernatant, add 10ml of distilled water, and place it in an ultrasonic cleaner to disperse the precipitate evenly. Add 2 ml of thioglycolic acid and continue to sonicate for 1 h.

(4) After filtering the product through a filter with a pore size of 220 nm, using a dialysis bag with a molecular weight cut-off of 500 Da, dialysis overnight, the dialysate is water, and the solution in the bag is collected to obtain the silver sulfide quantum dot stock solution.

Example 2

The present embodiment provides a silver sulfide quantum dot, and its preparation method is as follows:

(1) Dissolve 5mmol AgNO ₃ in 20ml deionized water to form a colorless and transparent solution, then under vigorous stirring, add concentrated ammonia water dropwise until the resulting brown precipitate completely disappears.

(2) The solution was transferred to the reaction kettle, 3 ml of dodecanethiol was added as the oil phase, and the solution was placed in an oven at 180°C for 3 hours.

(3) Collect the precipitate and discard the supernatant, add 10ml of distilled water, and place it in an ultrasonic cleaner to disperse the precipitate evenly. Add 2 ml of thioglycolic acid and continue to sonicate for 1 h.

(4) After filtering the product through a filter with a pore size of 220 nm, a dialysis bag with a molecular weight cut-off of 500 Da was used for overnight dialysis, the dialysate was water, and the solution in the bag was collected to obtain the silver sulfide quantum dot stock solution.

Example 3

The present embodiment provides a graphene hydrogel, and its preparation method is as follows:

40ml of silver sulfide quantum dot stock solution (prepared in Example 2) was mixed with 40mg of graphene oxide powder, and when the ultrasonic power was 150W, ultrasonic treatment was carried out with an ultrasonic cleaner for 0.5h to obtain silver sulfide quantum dots and graphene oxide. of the mixture. The mixed solution was transferred to a 50 mL polytetrafluoroethylene reaction kettle, and placed in an oven at 150° C. for 1 h to obtain a graphene hydrogel product.

The adsorption treatment of wastewater by the graphite hydrogel is as follows:

Take 6 parts of graphene hydrogels obtained according to the above method, each part is 30mg, and it is respectively 5mg/L, 40mg/L, 80mg/L, 120mg/L, 160mg/L, 200mg/L with a volume of 100ml. The methyl orange solution was mixed, and at a rotating speed of 200 r/min, vibrated and adsorbed with a magnetic stirrer for 1 h, and the temperature was 25 °C to complete the treatment of the methyl orange solution.

After the oscillating adsorption process, take 1 mL of solvent sample, use a 0.22 μm filter to remove the precipitate, and then measure the absorbance by an ultraviolet-visible spectrophotometer to determine the concentration of methyl orange after adsorption, and obtain the graphene hydrogel under this condition. The adsorption isotherm curve of orange is shown in Fig. Fig. 2 shows the fitting of the adsorption process using the Langmuir model. It can be seen that the linearity of the experimental data is good, the fitting residual R ² =0.9991, and the theoretical adsorption capacity is 263 mg/g.

Example 4

The present embodiment provides a graphene hydrogel, and its preparation method is as follows:

40ml of silver sulfide quantum dot stock solution (prepared in Example 2) was mixed with 40mg of graphene oxide powder, and under the condition of ultrasonic power of 150W, ultrasonic treatment was carried out with an ultrasonic cleaner for 0.5h to obtain silver sulfide quantum dots and graphene oxide. of the mixture. The mixed solution was transferred to a 50 mL polytetrafluoroethylene reaction kettle, and placed in an oven at 120° C. for 1 h to obtain a graphene hydrogel product.

The adsorption treatment of wastewater by the graphite hydrogel is as follows:

Take 6 parts of graphene hydrogels obtained according to the above method, each part is 30mg, and it is respectively 5mg/L, 40mg/L, 80mg/L, 120mg/L, 160mg/L, 200mg/L with a volume of 100ml. The methyl orange solution was mixed, and at a rotating speed of 200 r/min, vibrated and adsorbed with a magnetic stirrer for 1 h, and the temperature was 25 °C to complete the treatment of the methyl orange solution.

After the oscillating adsorption process, take 1 mL of solvent sample, use a 0.22 μm filter to remove the precipitate, and then measure the absorbance by UV-Vis spectrophotometer to determine the concentration of methyl orange after adsorption, and obtain the graphene hydrogel under this condition to methyl orange. The adsorption isotherm curve is shown in Fig. Figure 2 shows the fitting of the adsorption process using the Langmuir model. It can be seen that the experimental data has good linearity, the fitting residual R ² =0.9990, and the theoretical adsorption capacity is 292 mg/g.

Example 5

The present embodiment provides a graphene hydrogel, and its preparation method is as follows:

40ml of silver sulfide quantum dot stock solution (prepared in Example 2) was mixed with 40mg of graphene oxide powder, and under the condition of ultrasonic power of 150W, ultrasonic treatment was carried out with an ultrasonic cleaner for 0.5h to obtain silver sulfide quantum dots and graphene oxide. of the mixture. The mixed solution was transferred to a 50 mL polytetrafluoroethylene reaction kettle, and placed in an oven at 180° C. for 1 h to obtain a graphene hydrogel product.

The adsorption treatment of wastewater by the graphite hydrogel is as follows:

Take 6 parts of graphene hydrogels obtained according to the above method, each part is 30mg, it is respectively 100ml with volume, concentration is 5mg/L, 40mg/L, 80mg/L, 120mg/L, 160mg/L or 200mg/L. L of methyl orange solution was mixed, and at a rotational speed of 200 r/min, vibrated and adsorbed with a magnetic stirrer for 1 h, and the temperature was 25 °C to complete the treatment of the methyl orange solution.

After the oscillating adsorption process, take 1 mL of solvent sample, use a 0.22 μm filter to remove the precipitate, and then measure the absorbance by UV-Vis spectrophotometer to determine the concentration of methyl orange after adsorption, and obtain the graphene hydrogel under the modified conditions. The adsorption isotherm curve is shown in Fig. Figure 2 shows the fitting of the adsorption process using the Langmuir model. It can be seen that the experimental data has good linearity, the fitting residual R ² =0.9988, and the theoretical adsorption capacity is 227 mg/g.

Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (13)

1. a preparation method of graphene hydrogel, is characterized in that, comprises the steps: silver sulfide quantum dot stoste is mixed with graphene oxide, at 100-300 ℃, heat 0.5～10h, obtain final product; Wherein, the preparation method of described silver sulfide quantum dot stock solution is specifically: make Ag inorganic salt and dodecane mercaptan under alkaline condition, utilize hydrothermal synthesis method to make oil-soluble silver sulfide quantum dot, then use thioglycolic acid Surface functional group modification is performed on the oil-soluble silver sulfide quantum dots to obtain the silver sulfide quantum dot stock solution. 2 . The preparation method according to claim 1 , wherein the heating temperature is 120-180° C., and the heating time is 0.5-2 h. 3 . 3. preparation method according to claim 1, is characterized in that, the volume mass ratio of described silver sulfide quantum dot stoste and graphene oxide is 1mL:(0.1-10)mg. 4. preparation method according to claim 3, is characterized in that, the volume mass ratio of described silver sulfide quantum dot stoste and graphene oxide is 1mL:(0.5-3.5)mg. 5. preparation method according to claim 4, is characterized in that, the volume mass ratio of described silver sulfide quantum dot stoste and graphene oxide is 1mL:1mg. 6. The preparation method according to claim 1, wherein the silver sulfide quantum dot stoste is mixed with graphene oxide using ultrasound. 7. The preparation method according to claim 6, wherein the ultrasonic power is 50-500W, and the time is 0.1-10h. 8 . The preparation method according to claim 1 , further comprising: diluting the mixed solution before heating, and the dilution ratio is 0-20 times. 9 . 9. Application of the preparation method according to any one of claims 1 to 8 in the treatment of wastewater containing organic dyes. 10. The application according to claim 9, wherein the application specifically comprises the following steps: The graphene hydrogel is adsorbed with wastewater containing organic dyes; the rotation speed of the adsorption is 50-500r/min, the adsorption time is 0.1-10h, and the adsorption temperature is 0-45°C. 11 . The application according to claim 9 , wherein the mass-volume ratio of the graphene hydrogel to the organic dye-containing wastewater is (20-50) mg:100 mL. 12 . 12. The application according to claim 9, wherein the organic dye is methyl orange, methylene blue or rhodamine B. 13. The application according to claim 12, wherein the concentration of the organic dye is less than or equal to 1000 mg/L.