CN113896299A

CN113896299A - electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded biochar and preparation method and application thereof

Info

Publication number: CN113896299A
Application number: CN202111233160.7A
Authority: CN
Inventors: 魏佳; 徐梦蝶
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2022-01-07
Anticipated expiration: 2041-10-22
Also published as: CN113896299B

Abstract

The invention discloses an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded charcoal, and a preparation method and application thereof, and belongs to the technical field of advanced oxidation electro-Fenton in water treatment. The invention takes pyrolyzed biochar as a carrier, and ferromanganese layered double hydroxide (MnFe-LDH) is loaded on the surface of the biochar. The preparation method comprises the steps of mixing and stirring iron chloride, manganese chloride, urea, ammonium fluoride, biochar and water, carrying out hydrothermal reaction, washing and drying, mixing with ethanol and polytetrafluoroethylene, and coating on foamed nickel to form the MnFe-LDH @ BC electro-Fenton cathode material. The method has the advantages of simple process, convenient operation, low cost, high treatment efficiency, good removal effect, wide application range, high recycling rate, environmental protection, cleanness and no pollution, can be widely adopted, can efficiently remove pollutants in water, and has high application value and commercial value.

Description

electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded biochar and preparation method and application thereof

Technical Field

The invention belongs to the technical field of advanced oxidation of sewage treatment, and relates to a simple method for preparing an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded charcoal. More particularly, relates to a preparation method of an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded charcoal and application thereof in sewage treatment.

Background

In recent years, the removal of PPCPs from wastewater has attracted attention due to the potentially toxic effects of Pharmaceuticals and Personal Care Products (PPCPs) on humans and aquatic life. Antibiotics, which are a major class of PPCPs, are widely used in medicine and agriculture, but some of the unabsorbed antibiotics enter the ecosystem through medical waste water and domestic sewage. Advanced oxidation techniques (AOPs) have a significant effect on the removal of such refractory organics, and the electro-fenton method has received much attention from researchers. Oxygen is reduced at the cathode by an external electric field to generate hydrogen peroxide, and the obtained hydrogen peroxide reacts with Fe (II) in the solution to generate active oxygen substances to degrade pollutants. Therefore, the cathode material is a major factor limiting the development of the electro-fenton system.

At present, carbon materials such as graphite carbon, carbon sponge, graphite felt and reticular glassy carbon are considered as promising cathode materials due to the abundant reserves, excellent conductivity and good chemical stability. The biomass charcoal is a porous solid particulate matter with high aromaticity and rich carbon generated by thermochemical conversion of carbon-rich waste under oxygen-free or oxygen-deficient conditions. The composite material has rich pore structure, large specific surface area and more oxygen-containing active groups on the surface, however, the active sites of the original biochar are relatively limited, so that the degradation performance of the original biochar for catalyzing pollutants difficult to degrade is poor. Therefore, it is necessary to dope the biochar with appropriate heteroatoms to improve its catalytic performance.

Layered Double Hydroxides (LDHs) are a class of metal hydroxides consisting of two or more metal elements. Because of its strong anion exchange capacity, high redox activity and specific layered structure, it has attracted much attention as an electrochemical high-efficiency electrode material. Wherein the metals of the LDH (e.g., Fe, Co, Ni, Mn) are generally comprised of +2 and +3 valent transition metal cations, with these transition metals being associated with H₂O₂In situ reaction to generate active oxygen speciesThereby degrading the organic contaminants. Relatively speaking, it contains environmentally friendly metals such as Fe³⁺And Mn²⁺Has not been reported to be used for electro-Fenton reaction, and Fe element plays a relatively important role in electro-Fenton, and can not only react with H₂O₂Active oxygen substances are generated by in-situ reaction, and Fe circulation is formed, so that the reaction is continued conveniently. And the Mn ion can promote the interconversion of Fe because it has a high valence state.

However, LDH has some aggregation properties which significantly limit its catalyst activity. Thus, combining biochar with LDH improves the catalytic activity of biochar on the one hand and also improves the dispersibility of LDH on the other hand. The MnFe-LDH is loaded on the biochar, so that the physical and chemical synergistic effect of the two is enhanced, the transfer of electrons is promoted, the accumulation of the LDH is reduced, and more active sites are exposed.

Therefore, the development of the cathode material for the electro-fenton reaction of ferromanganese layered double hydroxide loaded biochar, which has simple and convenient process, easy industrialization and good characteristics, is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present invention aims to provide a preparation method of a manganese-iron layered double hydroxide loaded charcoal electro-fenton reaction cathode material, which is simple in process and easy for industrial production, for solving the problems existing in the prior art, and the material prepared by the method can treat persistent organic matters in water, has the advantages of high treatment efficiency, good removal effect, wide application range, high recycling rate, environmental protection, cleanness, no pollution, wide application range, wide material utilization, and high application value and commercial value.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded biochar specifically comprises the following steps:

(1) adding manganese chloride and ferrous chloride into water, stirring to dissolve completely, then adding urea, ammonium fluoride and pyrolyzed biochar, stirring and mixing to obtain a uniform solution for later use;

(2) placing the homogeneous solution in a reaction kettle for hydrothermal reaction, then alternately washing the product with deionized water and absolute ethyl alcohol for several times, and drying to obtain MnFe-LDH @ BC powder;

(3) mixing the MnFe-LDH @ BC powder with a polytetrafluoroethylene dispersion liquid and absolute ethyl alcohol, then performing ultrasonic dispersion uniformly to form a suspension, and heating to obtain a uniform paste substance;

(4) and (3) paving and pressing the uniform pasty substance on the pretreated foamed nickel, and finally drying to obtain the manganese-iron layered double hydroxide loaded charcoal electro-Fenton reaction cathode material.

Preferably, in the reaction system of step (1), the molar ratio of manganese chloride to ferrous chloride is 3: 1, the molar ratio of ferromanganese metal to urea to ammonium fluoride is 1: 5: 5, the doping amount of the biochar is 3-30% of the total mass of the ferromanganese metal, the urea and the ammonium fluoride.

Preferably, the hydrothermal reaction temperature in the step (2) is 100-140 ℃, and the reaction time is 6-12 h.

Preferably, in the step (3), the solid-to-liquid ratio of the MnFe-LDH @ BC powder, the polytetrafluoroethylene dispersion liquid and the ethanol is (0.1-0.6) g: (0.1-0.6) mL: (1-6) mL, and the mass concentration of the polytetrafluoroethylene dispersion is 55-65%.

Preferably, in the step (4), the foamed nickel substrate coated with the uniform pasty substance is dried at 105 ℃ for 0.5-1.5 h.

In conclusion, the invention provides a preparation method of the ferromanganese laminated double-metal hydroxide loaded charcoal electro-Fenton reaction cathode material, which is environment-friendly and suitable for industrial production.

The invention also claims the electro-Fenton reaction cathode material of the ferromanganese layered double hydroxide loaded biochar prepared by the method.

The invention also aims to provide the application of the electro-Fenton reaction cathode material of the ferromanganese layered double hydroxide loaded biochar in sewage treatment, which is green, environment-friendly and suitable for industrial production.

Specifically, the specific steps of treating sewage by the electro-Fenton cathode material with layered double hydroxide loading biochar are as follows: and (3) taking the layered double hydroxide loaded biochar as an electro-Fenton reaction cathode material, forming an electrode pair with an anode in an electrolytic cell, degrading the tetracycline-containing sewage under a direct current power supply, and exposing air to the sewage to carry out the electro-Fenton reaction, namely finishing the sewage treatment.

Further, the initial concentration of the tetracycline in the water body is less than or equal to 20 mg/L; the pH value of the tetracycline water body is 3-9; the direct current power supply keeps the current density at 5-25 mA.

According to the technical scheme, compared with the prior art, the electro-Fenton reaction cathode material with ferromanganese layered double hydroxide loaded with charcoal, the preparation method and the application thereof have the following excellent effects:

firstly, the invention utilizes the special layered structure of the layered double hydroxide and the good catalytic performance of the transition metal in the layered double hydroxide to load the layered double hydroxide on the biochar, and meanwhile, the biochar has good adsorption performance and electrical conductivity, contains abundant functional groups on the surface and can also enhance the dispersibility of the layered double hydroxide, so that the layered double hydroxide is used as a cathode plate of an electro-Fenton reaction to promote the electron transfer in the reaction process. In the reaction process, iron ions in the material and hydrogen peroxide form active oxygen substances to degrade pollutants. On the other hand, the existence of manganese ions leads the oxidation-reduction cycle conversion of iron ions to be carried out orderly, and the reaction is promoted to be continuously carried out, thereby finally achieving the good effect of removing pollutants.

Furthermore, the pH range of the solution is relatively wide, and the tetracycline removal rate can achieve a relatively good removal effect when the pH is 3-7; in addition, divalent iron ions do not need to be added additionally, so that the cost is saved, the influence of iron mud precipitation generated in the reaction process on the electro-Fenton reaction is avoided, the environment is prevented from being polluted, and the efficient green catalysis can be realized.

Secondly, the preparation method of the layered double hydroxide loaded biochar is simple, low in cost and environment-friendly, the electro-Fenton cathode material prepared by the method is good in tetracycline degradation capacity, and when the concentration of tetracycline is 20mg/L, the removal rate reaches 94.2%. Compared with biodegradation, membrane separation, oxidation reduction and photocatalysis, the method for degrading tetracycline by using the layered double hydroxide loaded biochar as the electro-Fenton cathode material has the advantages of simple operation and high degradation efficiency.

Finally, the biochar in the layered double hydroxide load biochar electro-Fenton cathode material prepared by the invention solves the problem of resource utilization of waste agricultural biochar and avoids the environmental problem caused by the accumulation of a large amount of agricultural waste straws.

Therefore, the preparation method disclosed by the invention has the advantages of simple preparation process, convenience in operation, low cost, high treatment efficiency, good removal effect, wide application range, high recycling rate, environmental friendliness, cleanness and no pollution, is a method which can be widely adopted and can efficiently remove pollutants in water, and has high application value and commercial value.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a scanning electron microscope image of an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide supported biochar.

FIG. 2 is an X-ray diffraction pattern of the electro-Fenton reaction cathode material with ferromanganese layered double hydroxide supporting biochar.

Fig. 3 is a graph comparing the degradation effect of the ferromanganese layered double hydroxide-supported biochar electro-fenton cathode material prepared in example 1 and the unloaded ferromanganese layered double hydroxide on tetracycline.

Fig. 4 is a graph comparing the degradation rate of the ferromanganese layered double hydroxide supported charcoal electro-fenton cathode material prepared in example 1 to tetracycline at different pH.

Fig. 5 is a graph comparing the degradation rate of the ferromanganese layered double hydroxide supported charcoal electro-fenton cathode material prepared in example 1 to tetracycline at different current densities.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention discloses a preparation method of an electro-Fenton reaction cathode material of ferromanganese layered double hydroxide loaded charcoal, which is green, environment-friendly, simple and convenient in process and suitable for industrial production.

The present invention will be further specifically illustrated by the following examples for better understanding, but the present invention is not to be construed as being limited thereto, and certain insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing disclosure are intended to be included within the scope of the invention.

The technical solution of the present invention will be further described with reference to the following specific examples.

Example 1:

(1) adding 2.7mmol of manganese chloride and 0.9mmol of ferrous chloride into 60ml of water, stirring to completely dissolve, adding 18mmol of urea, 18mmol of ammonium fluoride and 0.5g of biochar pyrolyzed at 600 ℃, and stirring and mixing uniformly;

(2) putting the solution obtained in the step (1) into a 100mL reaction kettle, and carrying out hydrothermal reaction for 6h at the temperature of 120 ℃;

(3) cooling the product after reaction to room temperature, and then alternately washing the product for a plurality of times by using deionized water and absolute ethyl alcohol, keeping the obtained precipitate at 80 ℃ for 12h, drying and dehydrating to obtain MnFe-LDH @ BC powder;

(4) mixing MnFe-LDH @ BC powder with 60% polytetrafluoroethylene dispersion liquid and absolute ethyl alcohol according to the mass concentration of 0.5 g: 0.5 mL: 5mL of the nickel foam is mixed in proportion, ultrasonic dispersion is carried out for 30min to obtain uniform electrode slurry, the electrode slurry is heated at the temperature of 80 ℃ to obtain a pasty substance, the nickel foam is ultrasonically soaked and cleaned for 2 times by acetone, and then the nickel foam is cleaned and dried by deionized water to finish pretreatment;

(5) and pressing the electrode paste on a pretreated foamed nickel substrate into a sheet with the thickness of 1mm, and finally drying the electrode at 105 ℃ to obtain the MnFe-LDH @ BC electro-Fenton reaction cathode plate.

(6) The electro-Fenton cathode and the Pt electrode form an electrode pair, and the electrode pair is placed in 50mM Na₂SO₄Adding tetracycline with initial concentration of 20mg/L into the electrolyte, adding 0.1mol/L NaOH and 0.1mol/L H₂SO₄Adjusting the pH value of the solution to 3.0, and adding 15mA of current; and after the electrolysis is finished, recovering the waste liquid and uniformly treating.

Example 2:

the same as example 1 except that 0.25g of biochar was mixed with the layered double hydroxide precursor.

Example 3:

the same as example 1, except that 1g of biochar was mixed with the layered double hydroxide precursor.

The electro-Fenton cathode materials prepared in examples 1-3 were tested against a control (biochar only) to remove tetracycline degradation from wastewater, and the results are shown in Table 1.

TABLE 1

Numbering	Degradation rate of tetracycline
		Example 1	94.16％
Example 2	89.94％
		Example 3	82.75％
Control group	66.96％

It can be seen that the doping amount of the biochar in the cathode material has a certain influence on the degradation rate of tetracycline, and firstly, it can be seen from a control group that pure biochar has a certain adsorption capacity on tetracycline, which is probably due to the large specific surface area and the pore structure. The removal rate of tetracycline is greatly improved by using the ferromanganese layered double hydroxide-loaded biochar as an electrode in example 1. And too little biochar is doped as in example 2, so that the ORR active sites on the surface of the material are few, and the degradation rate of tetracycline is low due to the sufficient transfer of electrons; too much biochar doping as in example 3 results in a reduced proportion of ferromanganese layered double hydroxide providing a reduced catalytic activity, while also affecting O due to too much impedance of the cathode material₂Mass transfer at the electrode surface, thereby affecting the tetracycline degradation rate.

Example 4:

the same as example 1 except that the solutions were electrolyzed while adjusting the pH values to 3, 5 and 7, respectively. The degradation rate of the electro-Fenton cathode material prepared in this example to tetracycline is shown in FIG. 4.

Example 5:

the electrolysis was carried out in the same manner as in example 1 except that the applied currents were set to 5, 15 and 25mA, respectively. The degradation rate of the electro-Fenton cathode material prepared in this example to tetracycline is shown in FIG. 5.

Fig. 1 is a scanning electron microscope image of the ferromanganese layered double hydroxide-loaded charcoal electro-fenton composite material prepared in example 1 of the present invention. As can be seen from fig. 1, the ferromanganese layered double hydroxide supported biochar appears like spherical particles, and the surface also shows a layered sheet structure.

FIG. 2 is an X-ray diffraction diagram of the ferromanganese layered double hydroxide supported charcoal electro-Fenton composite material prepared in example 1 of the present invention. As can be seen from fig. 2, the ferromanganese layered double hydroxide supported biochar electro-fenton composite retained almost all the main characteristic peaks (2 θ ═ 51.5 °,45.1 °,41.4 °,37.5 °,31.4 ° and 24.2 °) of the ferromanganese layered double hydroxide, thus demonstrating that the ferromanganese layered double hydroxide was successfully supported on the biochar surface.

Fig. 3 is a graph comparing the degradation effect of the ferromanganese layered double hydroxide-supported biochar electro-fenton cathode material prepared in example 1 and the unloaded ferromanganese layered double hydroxide on tetracycline. As can be seen from FIG. 3, the loaded ferromanganese layered double hydroxide biochar cathode degrades tetracycline by 94.16%, which is much higher than the degradation rate of the pure biochar cathode, and the effect of the loaded electrode in the experiment for simulating degradation of tetracycline in sewage is remarkable, which illustrates the effectiveness of ferromanganese layered double hydroxide loaded biochar as an electro-Fenton cathode for degradation of tetracycline in sewage.

Fig. 4 is a graph comparing the degradation rate of the ferromanganese layered double hydroxide supported charcoal electro-fenton cathode material prepared in example 1 to tetracycline at different pH. It can be seen that the tetracycline degradation rate was maintained at a relatively high level over a wide range of pH 3-7, with a maximum of 94.16% at pH 3. Therefore, compared with the traditional electro-Fenton, the material has a wider pH range, can better accept and treat pollutants in water, is not easy to generate iron mud, and is green and pollution-free.

Fig. 5 is a graph comparing the degradation rate of the ferromanganese layered double hydroxide supported charcoal electro-fenton cathode material prepared in example 1 to tetracycline at different current densities. It can be found that when the current is too small, the electric energy required by the electro-Fenton system cannot be provided, the oxygen reduction process is influenced, when the current is increased, the electron transfer speed on the surface of the electrode is accelerated, and the degradation of tetracycline is facilitated, but with the continuous increase of the current, side reactions such as cathodic hydrogen evolution or anodic oxygen evolution are accompanied, and the current efficiency and the degradation rate of tetracycline in electro-Fenton are reduced.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. a preparation method of the electro-Fenton reaction cathode material of ferromanganese layered double metal hydroxide loaded biochar, is characterized in that, described method specifically comprises the steps:

(1) in water, add manganese chloride and ferrous chloride, stir to dissolve completely, then add urea, ammonium fluoride and pyrolyzed biochar, stir and mix to obtain a homogeneous solution, for subsequent use;

(2) the homogeneous solution is placed in the reactor for hydrothermal reaction, then the product is alternately washed several times with deionized water and dehydrated alcohol, and dried to obtain MnFe-LDH@BC powder;

(3) mixing the MnFe-LDH@BC powder with a polytetrafluoroethylene dispersion liquid and anhydrous ethanol, then ultrasonically dispersing it uniformly to form a suspension, and heating to obtain a uniform paste substance;

(4) pressing the uniform paste-like substance onto the pretreated nickel foam, and finally drying to obtain the electro-Fenton reaction cathode material of ferromanganese layered double metal hydroxide-loaded biochar.

2. the preparation method of the electro-Fenton reaction cathode material of a kind of ferromanganese layered double metal hydroxide loaded biochar according to claim 1, is characterized in that, in the reaction system of described step (1), chlorine The molar ratio of manganese to ferrous chloride is 3:1, the molar ratio of ferromanganese metal to urea and ammonium fluoride is 1:5:5, and the doping amount of biochar is the total of ferromanganese metal, urea and ammonium fluoride. 3%-30% of the mass.

3. the preparation method of the electro-Fenton reaction cathode material of a kind of ferromanganese layered double metal hydroxide loaded biochar according to claim 1, is characterized in that, the hydrothermal reaction temperature in described step (2) The temperature is 100℃～140℃, and the reaction time is 6～12h.

4. the preparation method of the electro-Fenton reaction cathode material of a kind of ferromanganese layered double metal hydroxide loaded biochar according to claim 1, is characterized in that, in described step (3), MnFe-LDH@ The solid-to-liquid ratio of BC powder, polytetrafluoroethylene dispersion and ethanol is (0.1-0.6) g: (0.1-0.6) mL: (1-6) mL, and the mass concentration of the polytetrafluoroethylene dispersion is 55% to 65%.

5. the preparation method of the electro-Fenton reaction cathode material of a kind of ferromanganese layered double metal hydroxide loaded biochar according to claim 1, is characterized in that, in described step (4), will be coated with The foamed nickel substrate with a uniform paste substance is dried at 105°C for 0.5 to 1.5 hours.

6 . An electro-Fenton reaction cathode material of ferromanganese layered double metal hydroxide loaded biochar prepared by any one of the methods of claims 1 to 5 .

7. An electro-Fenton reaction cathode material of the ferromanganese layered double metal hydroxide loaded biochar prepared by the method according to claim 1 or the ferromanganese layered double metal hydroxide loaded as claimed in claim 6 Electro-Fenton Reaction Cathode Materials of Biochar for Wastewater Treatment.

8 . The application according to claim 7 , wherein the specific step of treating sewage with the layered double metal hydroxide-loaded biochar electro-Fenton cathode material is: loading the layered double metal hydroxide with biological As the cathode material of the electro-Fenton reaction, carbon forms an electrode pair with the anode in the electrolytic cell, and under the DC power supply, the water body containing tetracycline is degraded, and the air is exposed to the sewage to carry out the electro-Fenton reaction, that is, the treatment of the sewage is completed. .

9. The application according to claim 8, wherein the initial concentration in the tetracycline water body is less than or equal to 20 mg/L; the pH value of the tetracycline water body is 3-9; the DC power supply maintains a current density of 5- 25mA.