CN105148964B - A kind of three-dimensional redox graphene Mn3O4/MnCO3Nano composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of three-dimensional redox graphene Mn₃O₄/MnCO₃Nano composite material and preparation method thereof, its molecular formula expression formula is RGO Mn₃O₄/MnCO₃, it is by graphene oxide and Mn₃O₄There is the nanocatalyst that photocatalysis is responded formed by hydro-thermal process.Under the induction of visible ultraviolet light, 100 milliliters of concentration can be 10 by 50 mg catalyst^‑5The methylene blue of mol/L is degradable in 90 minutes, and this catalyst has good adsorption effect to arsenic ion.It is an advantage of the invention that：1st, catalyst of the invention is that synthetic method is simple, and low production cost, the yield synthesized are higher, and purity is also very high and reproducible, are adapted to the requirement of extension production；2nd, catalyst has preferable photocatalysis degradation organic contaminant and heavy metal ion adsorbed performance.

Description

A three-dimensional reduced graphene oxide-Mn3O4/MnCO3 nanocomposite material and its preparation preparation method

technical field

The invention relates to a three-dimensional nano composite material reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ for photocatalytic degradation of organic pollutants and simultaneous removal of heavy metal ions in water and a preparation method thereof.

Background technique

Energy is one of the indispensable material foundations for the development of human society and a prerequisite for human survival and development. However, as conventional fossil energy, namely oil, coal and natural gas, most of them are non-renewable energy, and their reserves are decreasing day by day, and they will be exhausted in the foreseeable short period of time. Human beings are facing a serious energy crisis. . With the increasingly serious energy problems, environmental pollution has gradually become prominent, and the process of industrialization and urbanization has been accelerating, environmental risks have increased sharply, and national environmental security has been challenged. The pollution of water resources is one of the most prominent environmental problems, and it is also one of the problems that countries all over the world are currently facing and need to be solved urgently. A wide variety of organic pollutants are not easy to decompose after entering the water body, and can exist in the water body stably for a long time. Most of them are toxic in themselves. "The effect poses a huge threat to human health. For these refractory organic pollutants, especially persistent organic pollutants (POPs), it is difficult to remove them by traditional physical, chemical and biological treatment processes. Therefore, how to rationally use energy and economically and effectively control and treat refractory organic pollutants in water is particularly urgent.

The photocatalytic degradation method started in 1972 and is a new method of sewage treatment developed in the past 30 years. The photocatalytic degradation method can effectively degrade a variety of organic pollutants and mineralize all organic substances into CO ₂ , H ₂ O or less toxic organic substances, which can completely destroy organic substances and meet the requirements of harmless treatment. However, due to the wide bandgap (3.2 eV) of TiO ₂ , it can only respond to ultraviolet light below 387.5 nanometers, and the utilization efficiency of visible light, which accounts for most of the solar spectrum, is low, which limits the industrial application of nano-TiO ₂ . Therefore, it is of great significance to develop efficient visible light-induced photocatalysts. The synthesis method of trimanganese tetraoxide is simple, the raw material is cheap, and it has good absorption of visible light, which has become another hot spot of people's research, and graphene with excellent characteristics is introduced into the photocatalyst to form a multi-component photocatalyst with trimanganese tetraoxide. The heterojunction will be more conducive to improving the properties of the catalyst and improving its photocatalytic degradation of organic matter.

The development of semiconductor photocatalytic degradation of organic pollutants technology can not only make full use of solar energy, a huge, pollution-free, clean and safe renewable energy, to achieve the purpose of energy saving, but also effectively degrade organic pollutants and play a role in environmental protection. Therefore, the development of visible light responsive, efficient and stable photocatalysts is the key to solving the widespread application of photocatalysis in water pollution control.

Contents of the invention

The purpose of the present invention is to provide a new photocatalytic degradation of organic pollutants and synchronous removal of heavy metal ions in water three-dimensional nanocomposite reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ , which provides a new material for solving today's environmental problems. The preparation of the material of the present invention is to obtain three-dimensional graphene-loaded nanomaterials through condensation reflux and hydrothermal treatment, which has simple operation, low production cost, high synthesis yield, high purity and good repeatability, and is suitable for expansion. production requirements.

The present invention is achieved in this way, a three-dimensional reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ nanocomposite material is characterized in that: the material is made of reduced graphene oxide (RGO), Mn ₃ O ₄ and MnCO ₃ The composition of the composite material, whose molecular formula is expressed as RGO-Mn ₃ O ₄ /MnCO ₃ ; under the irradiation of a 300-watt xenon lamp, in the absence of noble metal co-catalysis, 50 mg of reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ The nanocomposite material can completely degrade 100 ml of methylene blue with a concentration of 10 ^-5 mol/L within 90 minutes, and has a good adsorption effect on arsenic ions.

The catalyst RGO-Mn ₃ O ₄ /MnCO ₃ of the present invention can change the pH to obtain RGO-Mn ₃ O ₄ /MnCO ₃ nanometer photocatalysts with different composition ratios.

Catalyst RGO-Mn _of the present invention O ₄ /MnCO _The preparation method is:

(1) Weigh 1-3 grams of manganese acetate into a 25 ml beaker, add 5-10 ml of deionized water and place in an ultrasonic cleaner to ultrasonically dissolve until clarification, transfer to a 250 ml three-necked flask and reflux and stir;

(2) Then add 6~130 ml of ethanol dropwise at 45°C, add 5~10 ml of ammonia water dropwise after about 15 minutes, raise the temperature to 80°C for 3 hours after the addition, centrifuge, wash, and vacuum dry;

(3) Disperse 200 mg of the dried sample in 15 ml of graphene oxide with a concentration of 4.6 g/L, stir for 15 minutes to disperse evenly, adjust the pH of the solution to 3.5~9.5, and fill the resulting solution into 25 ml of poly Put the reaction kettle of tetrafluoroethylene into the muffle furnace at 150-200 ℃ for hydrothermal reaction for 12 hours.

(4) The sample after the hydrothermal reaction was filtered, washed, and freeze-dried several times to obtain the target catalyst.

The advantages of the present invention are: 1. The multi-component nanomaterial is the first reported layered graphite oxide as the base material, and the optimal ratio is controlled by adjusting the pH of the solution to synthesize a photocatalytic degradation of organic matter with a ternary nanostructure. 2, the catalyst of the present invention adopts the reflux-hydrothermal method to synthesize, and its operation is simple, the production cost is cheap, the productive rate of synthesis is higher, and the purity is also very high and repeatability is good, is suitable for the requirement of expanding production; 3, has Better performance in photocatalytic degradation of organic pollutants and removal of heavy metals.

Description of drawings

Fig. 1 is an X-ray powder diffraction pattern of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention.

Fig. 2 is the Raman diagram of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention

Fig. 3 is a scanning electron micrograph of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention.

Fig. 4 is a comparison diagram of the degradation effect of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention in the degradation of methylene blue under simulated sunlight.

Fig. 5 is a full band scanning diagram of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention.

Fig. 6 is a comparison chart of heavy metal adsorption and oxidation of the RGO-Mn ₃ O ₄ /MnCO ₃ catalyst of the present invention.

detailed description

The embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, but the present embodiments are not intended to limit the present invention, and any similar structures and similar changes of the present invention should be included in the protection scope of the present invention.

Synthesis of Catalyst RGO-Mn ₃ O ₄ /MnCO ₃ :

1. Synthesis of compound Mn ₃ O ₄

Weigh 1.5 g of Mn(Ac) ₂ .4H ₂ O into a 25 ml beaker, add 6 ml of H ₂ O and place it in an ultrasonic cleaner to ultrasonically dissolve until clarified, transfer to a 250 ml three-necked flask and stir at reflux, Then at 45°C, 100 ml of ethanol was added dropwise, and after about 15 mins, 7.5 ml of ammonia water was added dropwise. After the dropwise addition, the temperature was raised to 80°C for 3 hours of reaction, centrifuged, washed, and dried in vacuum.

2. Synthesis of catalyst RGO-Mn ₃ O ₄ /MnCO ₃ at pH=3.5

Disperse 200 mg of the dried sample in 15 ml of graphene oxide, stir for 15 minutes to disperse evenly, and then adjust the pH of the solution to 3.5, put the resulting solution into a 25 ml polytetrafluoroethylene reactor, and put Into a muffle furnace at 180°C for hydrothermal reaction for 12 hours. The sample after the hydrothermal reaction was filtered, washed, and freeze-dried several times to obtain the target catalyst.

3. Synthesis of catalyst RGO-Mn ₃ O ₄ /MnCO ₃ at pH=7.5

Disperse 200 mg of the dried sample in 15ml of graphene oxide, stir for 15 minutes to disperse evenly, and then adjust the pH of the solution to 7.5, put the resulting solution into a 25 ml polytetrafluoroethylene reactor, and put Hydrothermal reaction in a muffle furnace at 200°C for 12 hours. The sample after the hydrothermal reaction was filtered, washed, and freeze-dried several times to obtain the target catalyst.

4. Synthesis of catalyst RGO-Mn ₃ O ₄ /MnCO ₃ at pH=8.0

Disperse 200 mg of the dried sample in 15 ml of graphene oxide, stir for 15 minutes to disperse evenly, and then adjust the pH of the solution to 8.0, put the resulting solution into a 25 ml polytetrafluoroethylene reactor, and put Hydrothermal reaction in a muffle furnace at 180°C for 12 hours. The sample after the hydrothermal reaction was filtered, washed, and freeze-dried multiple times to obtain the target catalyst

5. Synthesis of catalyst RGO-Mn ₃ O ₄ /MnCO ₃ at pH=9

Disperse 200 mg of the dried sample in 15ml of graphene oxide, stir for 15 minutes to disperse evenly, adjust the pH of the solution to 9 respectively, put the resulting solution into a 25 ml polytetrafluoroethylene reactor, put Hydrothermal reaction in a muffle furnace at 200°C for 12 hours. The sample after the hydrothermal reaction was filtered, washed, and freeze-dried multiple times to obtain the target catalyst

6. Synthesis of catalyst RGO-Mn ₃ O ₄ /MnCO ₃ at pH=9.5

Disperse 200 mg of the dried sample in 15ml of graphene oxide, stir for 15 minutes to disperse evenly, and then adjust the pH of the solution to 9.5, put the resulting solution into a 25 ml polytetrafluoroethylene reactor, put Hydrothermal reaction in a muffle furnace at 180°C for 12 hours. The sample after the hydrothermal reaction was filtered, washed, and freeze-dried several times to obtain the target catalyst.

As shown in Figure 1, the X-ray powder diffraction test results show that the diffraction pattern of the catalyst of the present invention is a composite material (RGO-Mn ₃ O ₄ /MnCO ₃ ) combined with a ternary compound, and its MnCO ₃ standard card JCPDS NO . 01-086-0173 and Mn ₃ O ₄ standard card JCPDS No. 00-024-0734 can correspond to the peak positions of the synthesized samples one by one. However, there is no graphene peak in the diffraction pattern, which is due to the fact that the amount of graphene is too small, or that the degree of disorder increases due to the uniform dispersion of graphene.

As shown in Figure 2, the Raman spectrum results further show that the graphene oxide in the catalyst sample is reduced to obtain graphene, and the Raman spectrum characteristic peaks of GO, Mn ₃ O ₄ and RGO-Mn ₃ O ₄ /MnCO ₃ All of them correspond one-to-one, indicating that Mn ₃ O ₄ and MnCO ₃ are successfully supported on the reduced graphene oxide, and the slight change in the peak position is caused by the bonding of graphene to it.

As shown in Figure ₃ , it can be clearly seen from the electron microscope that after combining with reduced graphene _oxide , the phenomenon of its own trimanganese tetroxide agglomeration is reduced _. The uniform radius is approximately 6 nm composed of particles. Figures (E) and (F) are electron diffraction and lattice fringe analysis. The lattice fringes with a width of 0.18nm, 0.25 nm, and 0.14 nm conform to the lattice fringes of Mn ₃ O ₄ , while the lattice fringes with a width of 0.4nm It is in line with the lattice fringes of MnCO ₃ , so we can infer that we have successfully synthesized the optimal ratio of trimanganese tetroxide and manganese carbonate loaded on graphene!

As shown in Figure 4, it is the degradation of methylene blue itself under light (blank), the degradation of methylene blue by trimanganese tetraoxide (Mn ₃ O ₄ ), and the degradation of methylene blue by composite photocatalytic materials synthesized at different pH (pH=3.5 , pH=7.5, pH=8.0, pH=9.0, pH=9.5). When pH=3.5, its catalytic effect is basically completely degraded within 90 mins!

As shown in Figure 5, we can clearly see through full-band scanning of the degraded filtrate that as time goes on, its intensity gradually decreases, and no other new peaks appear, indicating that our synthesized materials are sensitive to methyl blue. It has reached a complete mineralization effect, but not a process of mutual transformation or trade-off.

As shown in Figure 6, the concentration of As ⁵⁺ in the filtrate shows that the concentration of As ⁵⁺ in the filtrate is very low, about 200 ppb, and the concentration of As ³⁺ in the solution is reduced from 4000 ppb to about 200 ppb by adsorption and oxidation 500 ppb, the total content of arsenic in the solution was reduced to less than 500 ppb through the adsorption and oxidation of the composite photocatalytic material. From the adsorption of As ⁵⁺ , it can be seen that the RGO-Mn ₃ O ₄ /MnCO ₃ composite photocatalytic material has a good adsorption effect on As ⁵⁺ .

Claims (1)

1. a kind of preparation method of three-dimensional reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ nanocomposites, it is characterized in that, this material is to be made up of reduced graphene oxide, Mn ₃ O ₄ and MnCO ₃ composite material, in In the absence of noble metal co-catalysis, 50 mg of reduced graphene oxide-Mn ₃ O ₄ /MnCO ₃ nanocomposites can completely degrade 100 ml of methylene blue with a concentration of 10 ^-5 mol/L within 90 minutes. Arsenic ions have better adsorption effect; The preparation method steps of this material are as follows: (1) Weigh 1~3g of manganese acetate into a 25ml beaker, add 5~10ml of deionized water and place in an ultrasonic cleaner to ultrasonically dissolve until clarified, transfer to a 250ml three-necked flask and reflux and stir; (2) Then add 6~130ml of ethanol dropwise at 45°C, add 5~10ml of ammonia water dropwise after 15 minutes, raise the temperature to 80°C for 3 hours after the addition, centrifuge, wash, and vacuum dry; (3) Disperse 200 mg of the dried sample in 15 ml of graphene oxide with a concentration of 4.6 g/L, stir for 15 minutes to disperse evenly, adjust the pH of the solution to 3.5, and fill the resulting solution into 25 ml of polytetrafluoroethylene Put it into a muffle furnace at 150~200℃ for hydrothermal reaction for 12 hours; (4) The sample after the hydrothermal reaction was filtered, washed, and freeze-dried several times to obtain the target catalyst.