Background
The rare earth elements become a plurality of high-tech, traditional and future industry irreplaceable advanced materials such as super magnets, superconducting materials, chemical sensors, lasers, optical fibers, light emitting batteries, computer hard disks and the like due to unique magnetic, chemical, optical, catalytic and electrical properties of the rare earth elements. The tremendous development of emerging advanced technologies has led to an excessive demand for rare earths, and the limited resources have led to the expensive price of rare earths in the international market. In addition, such a situation causes more mining sites, and the mining of a large amount of rare earth elements causes a large amount of waste residues and waste water to be accumulated in the mining process, thereby seriously polluting the surrounding environment. If the wastewater is randomly discharged and not effectively recovered, a large amount of rare earth elements are lost and human health may be harmed. Therefore, further enrichment and recovery of valuable rare earth elements from aqueous solutions is indispensable in environmental and technical requirements. To solve these problems, various methods for separating and recovering rare earth from an aqueous solution have been proposed, including chemical precipitation, solvent extraction, ion exchange and electrochemical methods. However, most of these methods involve complicated procedures, high chemical toxicity, expensive energy consumption, and are effective only at high concentrations of rare earth ions. Therefore, it is very urgent and indispensable to develop an environment-friendly, low-cost technology for the sustainable supply of rare earth elements to enrich and recover rare earth elements. The adsorption method is simple and convenient to operate, flexible in design, non-toxic and easy to recover, and is generally regarded as an economic, environment-friendly and efficient rare earth ion recovery technology. Various adsorbents including clay, zeolite, activated carbon, chitosan, beta-cyclodextrin, silica, nanocomposite and the like have been widely used for the adsorption recovery of rare earth elements.
In order to further improve the separation and enrichment capacity of the adsorbent to rare earth elements, the research of an adsorption material which is simple to prepare, good in adsorption capacity, easy to recover and good in recycling performance is urgent.
Disclosure of Invention
The invention provides a three-dimensional graphene oxide composite material and a preparation method and application thereof, and aims to provide a composite material which is simple to prepare, good in adsorption capacity, easy to recover and good in recycling performance and a preparation method thereof, so that the rare earth ions in an aqueous solution can be effectively enriched and recovered.
In order to achieve the above object, the present invention provides a method for preparing a three-dimensional graphene oxide composite material, comprising the following steps:
step 1: preparing a graphene oxide solution by using crystalline flake graphite as a raw material;
step 2: and (2) adding 2-aminobenzothiazole into the graphene oxide solution obtained in the step (1), stirring, ultrasonically mixing uniformly, then carrying out self-assembly reaction at high temperature and high pressure, and freeze-drying to obtain the composite material.
Preferably, in the step 1, a graphene oxide solution of 3-12 mg/mL is prepared by using a modified Hummers method.
Preferably, in the step 2, the mass ratio of the graphene oxide to the 2-aminobenzothiazole is 1: 1-30: 1.
Preferably, in the step 2, the stirring time is 1-20 min, and the ultrasonic time is 5-60 min.
Preferably, in the step 2, the high-temperature and high-pressure conditions are provided by an oven and a high-temperature and high-pressure reaction kettle, the reaction temperature is 100-200 ℃, and the reaction time is 2-10 hours.
Preferably, in the step 2, after the reaction is completed, the reaction product is naturally cooled to room temperature, ultrapure water is added into the obtained composite material until the product concentration is 10-20 mg/mL, the composite material is transferred to a quick freezing machine at-50 ℃ for quick freezing, and finally the composite material is transferred to a vacuum freeze drying machine for drying.
The invention also provides the three-dimensional graphene oxide composite material prepared by the method.
The invention also provides an application of the three-dimensional graphene oxide composite material in efficient recovery of rare earth ions in an aqueous solution.
Preferably, the rare earth ions are corresponding chloride salts, and the concentration of the adsorbate is 1-100 mg/L.
Preferably, the rare earth ions include lanthanum ions, erbium ions, ytterbium ions, neodymium ions and yttrium ions.
The scheme of the invention has the following beneficial effects:
according to the invention, 2-aminobenzothiazole interacts with graphene oxide under high temperature and high pressure through pi-pi action and hydrogen bonds to generate the aerogel composite material with a three-dimensional structure, and the three-dimensional aerogel composite material is formed by utilizing the interpenetration action of organic molecules 2-aminobenzothiazole and the non-covalent bond acting force between the organic molecules and the graphene oxide. The composite material reserves rich oxygen-containing functional groups (carboxyl and hydroxyl) on the surface of graphene oxide and sulfur-nitrogen heteroatoms and amino on 2-aminobenzothiazole molecules as adsorption active sites for rare earth ions, and the adsorption recognition capability of the composite material for the rare earth ions is effectively improved by introducing the amino of 2-aminobenzothiazole and the nitrogen-sulfur heteroatoms on the surface of the graphene oxide.
The aerogel structure of the three-dimensional graphene oxide composite material can effectively avoid the agglomeration of a graphene oxide substrate, can realize the regeneration and recycling performance in the adsorption process, and can greatly reduce the cost of the adsorption material. The composite material is expected to become an advanced adsorption material for enriching and recycling rare earth, which is widely applied.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
Example 1
The preparation method of the three-dimensional graphene oxide composite material in the present example is as follows:
preparing a graphene oxide solution by using crystalline flake graphite as a raw material and adopting an improved Hummers method, and diluting the graphene oxide solution to 5mg/mL for later use.
50mg of 2-aminobenzothiazole were weighed out for further use.
And adding 10mL of graphene oxide solution into 2-aminobenzothiazole, stirring for 15min, and performing mixing ultrasonic treatment for 40min to obtain a uniformly mixed dispersion liquid.
And (3) moving the mixed dispersion liquid to a high-temperature high-pressure reaction kettle, carrying out hydrothermal reaction for 4h at the temperature of 140 ℃, and naturally cooling to room temperature for later use.
And adding 20mL of ultrapure water into the obtained composite material, transferring the composite material to a quick freezer at the temperature of-50 ℃ for quick freezing, and finally transferring the composite material to a vacuum freeze dryer for drying to obtain the three-dimensional graphene oxide composite material.
Example 3
The preparation method of the three-dimensional graphene oxide composite material in the present example is as follows:
preparing a graphene oxide solution by using crystalline flake graphite as a raw material and adopting an improved Hummers method, and diluting the graphene oxide solution to 5mg/mL for later use.
5mg of 2-aminobenzothiazole were weighed out for further use.
And adding 10mL of graphene oxide solution into 2-aminobenzothiazole, stirring for 10min, and performing ultrasonic mixing for 20min to obtain a uniformly mixed dispersion liquid.
And (3) moving the mixed dispersion liquid to a high-temperature high-pressure reaction kettle, carrying out hydrothermal reaction for 4h at the temperature of 100 ℃, and naturally cooling to room temperature for later use.
And adding 20mL of ultrapure water into the obtained composite material, transferring the composite material to a quick freezer at the temperature of-50 ℃ for quick freezing, and finally transferring the composite material to a vacuum freeze dryer for drying to obtain the three-dimensional graphene oxide composite material.
Example 4
The preparation method of the three-dimensional graphene oxide composite material in the present example is as follows:
preparing a graphene oxide solution by using crystalline flake graphite as a raw material and adopting an improved Hummers method, and diluting the graphene oxide solution to 5mg/mL for later use.
3.33mg of 2-aminobenzothiazole were weighed out for further use.
And adding 10mL of graphene oxide solution into 2-aminobenzothiazole, stirring for 5min, and performing ultrasonic mixing for 15min to obtain a uniformly mixed dispersion liquid.
And (3) moving the mixed dispersion liquid to a high-temperature high-pressure reaction kettle, carrying out hydrothermal reaction for 3h at 160 ℃, and naturally cooling to room temperature for later use.
And adding 20mL of ultrapure water into the obtained composite material, transferring the composite material to a quick freezer at the temperature of-50 ℃ for quick freezing, and finally transferring the composite material to a vacuum freeze dryer for drying to obtain the three-dimensional graphene oxide composite material.
Example 5
The preparation method of the three-dimensional graphene oxide composite material in the present example is as follows:
preparing a graphene oxide solution by using crystalline flake graphite as a raw material and adopting an improved Hummers method, and diluting the graphene oxide solution to 5mg/mL for later use.
2.5mg of 2-aminobenzothiazole were weighed out for further use.
And adding 10mL of graphene oxide solution into 2-aminobenzothiazole, stirring for 5min, and performing ultrasonic mixing for 10min to obtain a uniformly mixed dispersion liquid.
And (4) moving the mixed dispersion liquid to a high-temperature high-pressure reaction kettle, carrying out hydrothermal reaction for 8h at the temperature of 120 ℃, and naturally cooling to room temperature for later use.
And adding 20mL of ultrapure water into the obtained composite material, transferring the composite material to a quick freezer at the temperature of-50 ℃ for quick freezing, and finally transferring the composite material to a vacuum freeze dryer for drying to obtain the three-dimensional graphene oxide composite material.
Example 6
The preparation method of the three-dimensional graphene oxide composite material in the present example is as follows:
preparing a graphene oxide solution by using crystalline flake graphite as a raw material and adopting an improved Hummers method, and diluting the graphene oxide solution to 5mg/mL for later use.
3.3mg of 2-aminobenzothiazole were weighed out for further use.
And adding 10mL of graphene oxide solution into 2-aminobenzothiazole, stirring for 5min, and performing ultrasonic mixing for 15min to obtain a uniformly mixed dispersion liquid.
And (4) moving the mixed dispersion liquid to a high-temperature high-pressure reaction kettle, carrying out hydrothermal reaction for 6h at the temperature of 120 ℃, and naturally cooling to room temperature for later use.
And adding 20mL of ultrapure water into the obtained composite material, transferring the composite material to a quick freezer at the temperature of-50 ℃ for quick freezing, and finally transferring the composite material to a vacuum freeze dryer for drying to obtain the three-dimensional graphene oxide composite material.
The three-dimensional graphene oxide composite material prepared in example 6 was used to adsorb rare earth ions in an aqueous solution, and lanthanum ions (La), erbium ions (Er), ytterbium ions (Yb), neodymium ions (Nd), and yttrium ions (Y) were selected to perform adsorption experiments, respectively. And analyzing the morphology, chemical composition and bonding mode of the material by adopting a scanning electron microscope, a Fourier infrared spectrum and an X-ray photoelectron spectrum. The adsorption results and the characterization of the materials are shown in FIGS. 1-2.
Fig. 1a shows that the three-dimensional graphene oxide composite material becomes a complete three-dimensional columnar structure after being dried, and a scanning electron microscope image shows that the structure of the composite material becomes a large unfolded sheet layer with few folds. From fig. 1b, the three-dimensional graphene oxide composite material has better adsorption capacity for several rare earth ions.
As can be seen from fig. 1C, the three-dimensional graphene oxide composite material is successfully synthesized, and due to pi-pi action and hydrogen bonding action between the 2-aminobenzothiazole and the functional group of the graphene oxide, compared with a characteristic absorption peak of pure graphene oxide, the hydroxyl (-OH) and carbonyl (-C ═ O) peaks of the three-dimensional graphene oxide composite material have obvious movement. Meanwhile, after the three-dimensional graphene oxide composite material adsorbs erbium ions (Er), hydroxyl (-OH) and carbonyl (-C ═ O) peaks obviously move to the low wave number direction, which shows that the composite material successfully adsorbs the erbium ions (Er).
Fig. 2 further shows the synthesis of the three-dimensional graphene oxide composite material and the adsorption of erbium ions (Er). From fig. 2a, the new combination energy of nitrogen (N) and sulfur (S) and the new combination energy of erbium (Er) after erbium ion adsorption of the composite material can be clearly seen. Respectively performing peak-splitting fitting on a nitrogen (N) element, an oxygen (O) element and a sulfur (S) element of the front-back three-dimensional graphene oxide-aromatic heterocyclic compound composite material for adsorbing erbium ions (see fig. 2 b-2 d). Performing peak-splitting fitting compared with nitrogen (N) element of the three-dimensional graphene oxide composite material before adsorption, and adsorbing erbium ions, as shown in figure 2b, -NH2And C-N ═ C peaks shift from 400.87 and 400.27eV to 400.68 and 399.76eV, respectively; the peak fitting plots of the oxygen (O) element before and after the adsorption of erbium ions showed that the carboxyl, hydroxyl and carbonyl peaks shifted from 533.52, 532.74 and 531.90eV to 533.53, 532.70 and 531.68eV, respectively (see fig. 2 c); fitting plots of the partial peaks of sulfur (S) before and after erbium ion adsorption showed that the C-S peak shifted from 164.61eV to 164,82eV (see fig. 2 d). These results indicate that the adsorption mechanism of the three-dimensional graphene oxide composite material to erbium ions is the complexation of free electrons of nitrogen, oxygen and sulfur of the composite material and erbium ions and the electrostatic attraction of carboxyl and erbium ions.
As can be seen from fig. 3, the three-dimensional graphene oxide composite material has an excellent recycling effect, and after 10 cycles of erbium ion adsorption-desorption, the adsorption rate of 100% and the elution rate of about 90% are still maintained.
The three-dimensional graphene oxide composite material prepared by the invention is simple to prepare, has a stable three-dimensional columnar structure, is good in reusability, has good adsorption performance on rare earth ions, and can realize effective adsorption and enrichment of the rare earth ions in an aqueous solution.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.