CN117303548A - Preparation method and application of micro-nano zero-valent iron/carbon composite material - Google Patents

Abstract

The invention discloses a preparation method and application of micro-nano zero-valent iron/carbon composite material. The material of this micro-nano zero-valent iron/carbon composite material includes porous carbon and zero-valent iron particles distributed inside or on the surface of the carbon material. The diameter of the zero-valent iron particles is ≤0.5 μm. The invention provides a method for preparing micro-nano zero-valent iron/carbon composite materials. The carbothermal reduction catalyst (auxiliary agent) sodium nitrate is added and then pyrolyzed, which can significantly reduce the pyrolysis temperature of zero-valent iron prepared by carbothermal reduction. Effectively increase the zero-valent iron content of carbothermal reduction at low temperature and reduce costs. The content of zero-valent iron in the micro-nano zero-valent iron/carbon composite material of the present invention is at least greater than 40%, which further improves the reaction activity. In addition, its surface is coated with a porous carbon carrier, which overcomes the technical shortcomings of traditional zero-valent iron that is easy to agglomerate, unstable, difficult to transport, and difficult to preserve.

Description

A preparation method and application of micro-nano zero-valent iron/carbon composite material

Technical field

The invention belongs to the field of environmentally friendly materials, and specifically relates to a preparation method and application of micro-nano zero-valent iron/carbon composite materials.

Background technique

Since its discovery in the 1990s, nanoscale zero-valent iron (nZVI) has been used in fields such as heavy metal pollution remediation and organic matter pollution remediation because of its environmental friendliness and wide range of uses. However, nanoscale zero-valent iron has shortcomings such as difficulty in maintaining high activity and complicated preparation process, which limits its further application. In recent years, some scholars have explored the preparation of nanoscale zero-valent iron through carbothermal reduction and applied it in the field of environmental remediation. The Fe ⁰ /C composite material prepared by carbothermal reduction can be widely used in the removal of heavy metals such as chromium (IV) and uranium (U) and organic matter such as antibiotics, dyes, and pesticides. On the one hand, carbothermal reduction solves the problems of preparation and preservation of zero-valent iron, and on the other hand, it introduces carbon materials to enhance the removal of pollutants. It can be applied in advanced oxidation processes to mineralize antibiotics and repair water pollution. The activation efficiency of Fe ⁰ /C composite materials is closely related to the content of zero-valent iron in the material. However, in the currently disclosed process, magnetic biochar prepared at low temperature usually does not contain zero-valent iron, while the content of zero-valent iron in composite materials prepared at high temperature is low, resulting in lower activation efficiency compared with nano zero-valent iron. It is necessary to improve the activation efficiency of carbothermally reduced Fe ⁰ /C composite materials by increasing the zero-valent iron content.

In addition, the reduction conditions and temperatures for preparing zero-valent iron through carbothermal reduction generally require relatively high temperatures. This is mainly because carbon needs to be pyrolyzed to trigger further reduction reactions, and iron species also need to undergo morphological changes. This also leads to the high temperature of carbothermal reduction, which increases the cost of preparing zero-valent iron. At present, lowering the pyrolysis temperature of carbothermal reduction is a direct way to increase the zero-valent iron content and effectively reduce costs. Therefore, there is an urgent need to develop a method to effectively reduce the pyrolysis temperature of carbothermal reduction.

Contents of the invention

In order to overcome the above-mentioned problems in the prior art, one of the purposes of the present invention is to provide a micro-nano zero-valent iron/carbon composite material. The second object of the present invention is to provide a preparation method of this micro-nano zero-valent iron/carbon composite material. The third object of the present invention is to provide the application of this micro-nano zero-valent iron/carbon composite material.

The inventor has verified many times that finding suitable catalysts or additives to reduce the pyrolysis temperature of carbothermal reduction is a direct way to effectively reduce costs.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

The first aspect of the present invention provides a micro-nano zero-valent iron/carbon composite material. The material includes porous carbon and zero-valent iron particles distributed inside or on the surface of the carbon material. The diameter of the zero-valent iron particles is ≤0.5 μm. .

Preferably, the particle size of the zero-valent iron particles distributed inside the porous carbon is 10-200 nm, and the particle size of the zero-valent iron particles distributed on the surface of the carbon material is 300-500 nm.

Preferably, the zerovalent iron content in the micro-nano zerovalent iron/carbon composite material is greater than 40%.

Preferably, the zero-valent iron particles are evenly dispersed in the gaps and surfaces of porous carbon and embedded in pores.

A second aspect of the present invention provides a method for preparing micro-nano zero-valent iron/carbon composite materials, which includes the following steps: mixing iron salts, biomass and catalysts, and performing a carbothermal reaction to prepare the micro-nano zero-valent iron/carbon composite material. Carbon composite material; the catalyst includes at least one of sodium salt, potassium salt or cryolite.

Preferably, the sodium salt is sodium nitrate, and the potassium salt is potassium nitrate.

More preferably, the catalyst is sodium nitrate.

Preferably, the biomass is at least one of straw, rice husk, sugarcane bagasse, coconut shell, distiller's grains, wood chips or bamboo chips. More preferably, the biomass is sugarcane bagasse.

Preferably, the iron salt is selected from at least one of iron nitrate, iron chloride or iron carbonate. More preferably, the iron salt is ferric nitrate.

Preferably, the mass ratio of the iron salt to biomass is 10: (1-5); and/or the mass ratio of the iron salt to the catalyst is 10: (0.01-0.6). More preferably, the mass ratio of the iron salt to biomass is 10: (2-4); and/or the mass ratio of the iron salt to the catalyst is 10: (0.1-0.4).

Preferably, the mixing method is solution mixing or ball milling mixing; and/or the solvent for solution mixing is water.

More preferably, the solution mixing method includes the following steps: uniformly mixing the iron salt, biomass and catalyst in water, and the mixing time is 0.5 to 12 hours.

Preferably, the conditions for the carbothermal reaction are selected from one or more of the following:

A) Heating rate 5～15℃/min;

B) Reaction temperature 600~900℃;

C) Reaction time 1 to 3 hours.

More preferably, the conditions for the carbothermal reaction are: heating to 600-900°C at a temperature rise rate of 5-15°C/min, maintaining for 1-3 hours, and then cooling to room temperature naturally. More preferably, the conditions for the carbothermal reaction are: heating to 700°C at a heating rate of 5°C/min, holding for 3 hours, and then cooling to room temperature naturally.

Preferably, the carbothermal reaction is carried out under a protective atmosphere. More preferably, the protective atmosphere is a nitrogen atmosphere.

The third aspect of the present invention provides the micro-nano zero-valent iron/carbon composite material described in the first aspect of the present invention or the micro-nano zero-valent iron/carbon composite material prepared by the preparation method described in the second aspect of the present invention. applications in.

Preferably, the polluted water body is mainly organic pollutants, and the organic matter is antibiotics. More preferably, the antibiotic includes at least one of metronidazole, brominated diphenyl ether, metronidazole, florfenicol, norfloxacin, tetracycline, and oxytetracycline.

The fourth aspect of the present invention provides a method for treating antibiotic-contaminated wastewater. Based on the application described in the third aspect of the present invention, the above-mentioned zero-valent iron/carbon composite material is used to treat antibiotic-containing contaminated wastewater.

Preferably, the method for treating antibiotic-contaminated wastewater specifically includes the following steps: adding the above-mentioned micro-nano zero-valent iron/carbon composite material and oxidants such as persulfate into the contaminated water body, mixing, and performing in-situ remediation. More preferably, the oxidizing agent such as persulfate is selected from at least one of peroxymonosulfate, peroxydisulfate or sodium sulfite.

More preferably, when the mass concentration of pollutants in the polluted water body is 1-100 mg/L, the dosage of the micro-nano Fe ⁰ /C composite material is 0.5-5 g/L, and the dosage of the oxidant is 1-100 mg/L. 5mM.

More preferably, the repair time is 1 to 100 minutes.

The beneficial effects of the present invention are:

The invention provides a method for preparing micro-nano zero-valent iron/carbon composite materials. The carbothermal reduction catalyst (auxiliary agent) sodium nitrate is added and then pyrolyzed, which can significantly reduce the pyrolysis temperature of zero-valent iron prepared by carbothermal reduction. Effectively increase the zero-valent iron content and reduce costs. In the electron transfer process of zero-valent iron, carbon materials can serve as electron transport carriers, and defects on the carbon materials can affect the generation of non-free radicals during the persulfate activation process. At the same time, due to the close combination of iron species and carbon materials in carbothermal reduction at high temperatures, its previous interaction with the oxidant is much stronger than that of magnetic biochar and liquid-phase reduced carbon-loaded zero-valent iron. The unique surface properties and electronic properties of carbon materials also show positive effects in electron shuttling and accumulation of organic pollutants. This mechanism is mainly attributed to the tight combination of Fe ⁰ and C in the composite material. It also shows that high temperature can rearrange the active sites, and recrystallization greatly increases the active site density and mesoporosity of Fe ⁰ /C.

Specifically, compared with the prior art, the present invention has the following advantages:

1) The present invention provides micro-nano zero-valent iron/carbon composite materials. Because their surfaces are covered with porous carbon carriers, they overcome the technical defects of traditional zero-valent iron being easy to agglomerate, unstable, difficult to transport, and difficult to preserve. The content of zero-valent iron in the micro-nano zero-valent iron/carbon composite material is at least greater than 40%. The unique surface properties and electronic properties of carbon materials also show positive effects in electron shuttling and accumulation of organic pollutants. At the same time, high temperature can rearrange the active sites, and recrystallization greatly increases the active site density and mesoporosity of Fe ⁰ /C, further improving the reaction activity.

2) The invention uses carbothermal reduction method to prepare micro-nano Fe ⁰ /C composite materials, which can reduce the temperature of zero-valent iron prepared by carbothermal reduction. The reaction conditions are simple, easy to operate, and convenient for industrialization. Under the action of carbothermal reduction catalyst (assistant) sodium nitrate, the zero-valent iron content is effectively increased and the cost is reduced. The preparation method can meet the industrial large-scale, low-cost production requirements.

3) The micro-nano Fe ⁰ /C composite material of the present invention has strong reactivity and can be used for environmental remediation. It only needs to directly add the micro-nano Fe ⁰ /C composite material of the present invention and persulfate to the polluted water body. Pollution remediation does not require other complicated devices and processes, and can be directly used in sewage treatment plants, which is easy to promote and apply. It can treat organic pollutants including metronidazole, florfenicol, norfloxacin, tetracycline, soil The removal of various antibiotics such as mycin and brominated diphenyl ether has good development prospects.

Description of the drawings

Figure 1 is an XRD pattern of micro-nano Fe ⁰ /C composite materials prepared by carbothermal reduction with different dosages of catalysts (auxiliaries) in Example 1 of the present invention;

Figure 2 is the XRD pattern of the micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction with or without catalyst (auxiliary agent) at different temperatures of the present invention;

Figure 3 is a graph showing the Fe ⁰ content of micro-nano Fe ⁰ /C composite materials prepared by carbothermal reduction with or without catalysts (auxiliaries) at different temperatures according to the present invention;

Figure 4 is an SEM image of Fe ⁰ /CB-Na@700 in Example 2 of the present invention;

Figure 5 is an SEM image of Fe ⁰ /CB-Na@800 in Example 2 of the present invention;

Figure 6 is an SEM image of Fe ⁰ /CB-Na@900 in Example 2 of the present invention;

Figure 7 is a TEM image of a micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction in Example 2 of the present invention, in which (a) is Fe ⁰ /CB-Na@700; (b) is Fe ⁰ /CB-Na@800 ; (c) is Fe ⁰ /CB-Na@900;

Figure 8 is an SEM image of a micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction in Comparative Example 1 of the present invention, in which (a) and (b) are images with different magnifications;

Figure 9 is a diagram showing the effect of micro-nano Fe ⁰ /C composite materials prepared by carbothermal reduction and nano zero-valent iron activated persulfate to remove antibiotics in Application Example 1 of the present invention;

Figure 10 is a diagram showing the effect of removing metronidazole by activating persulfate using different micro-nano Fe ⁰ /C composite materials prepared in Application Example 2 of the present invention;

Figure 11 is an analytical diagram of the intermediate products of the micro-nano Fe ⁰ /C composite activated persulfate to remove metronidazole in Application Example 3 of the present invention;

Figure 12 is a diagram showing the effect of removing various organic pollutants by activating persulfate to prepare micro-nano Fe ⁰ /C composite materials in Application Example 4 of the present invention.

Detailed ways

The content of the present invention will be further described in detail below through specific examples.

Example 1 Preparation of micro-nano zero-valent iron/carbon (Fe ⁰ /C) composite material

S1: Put 3.232g iron nitrate, 1.12g sugarcane bagasse passed through a 60 mesh sieve and 0.009g, 0.017g, 0.034g, 0.068g, 0.102g, 0.170g sodium nitrate respectively into a beaker with 50mL deionized water. Place the beaker on a magnetic stirrer and stir for 2 hours at a speed of 500 r/min. Then take out the solid material and dry it at 65°C for later use;

S2: Transfer the dried sample to a corundum ark, place it in a tube furnace, raise the temperature from room temperature to 900°C at 5°C/min and keep it for 180 minutes. The whole process is protected by nitrogen. After natural cooling, it is sieved to prepare micro Nano-Fe ⁰ /C composite materials are respectively recorded as Fe/CB _0.4 -Na _0.005 , Fe/CB _0.4 -Na _0.01 , Fe/CB _0.4 -Na _0.02 , Fe/CB _0.4 -Na _0.04 , and Fe/CB _0.4 -Na _0.06 and Fe/ _CB0.4 - _Na0.1 .

Example 2 Preparation of micro-nano zero-valent iron/carbon (Fe ⁰ /C) composite material

S1: Put 3.232g iron nitrate, 1.12g sugarcane bagasse passed through a 60-mesh sieve and 0.068g sodium nitrate into a beaker with 50mL deionized water, place the beaker on a magnetic stirrer and stir for 2 hours at a speed of 500r/min. Then take out the solid material and dry it at 65°C for later use;

S2: Transfer the dried sample to a corundum ark, place it in a tube furnace, and raise the temperature from normal temperature to 600°C, 700°C, 800°C, and 900°C at 5°C/min for 180 minutes. The entire process is protected by nitrogen. After natural cooling, it is sieved to obtain micro-nano Fe ⁰ /C composite materials, which are recorded as Fe/CB-Na@600, Fe/CB-Na@700, Fe/CB-Na@800 and Fe/CB-Na respectively. @900.

Comparative Example 1 Preparation of micro-nano zero-valent iron/carbon (Fe ⁰ /C) composite material

S1: Put 3.232g iron nitrate and 1.12g bagasse through a 60-mesh sieve into a beaker with 50mL deionized water. Place the beaker on a magnetic stirrer and stir for 2 hours at a speed of 500r/min. Then take out the solid matter and place it in the beaker. Dry at 65℃ for later use;

S2: Transfer the dried sample to a corundum ark, place it in a tube furnace, raise the temperature from room temperature to 900°C at 5°C/min and keep it for 180 minutes. The whole process is protected by nitrogen. After natural cooling, it is sieved to prepare micro Sodium Fe ⁰ /C composite material is recorded as Fe/CB _0.4 .

Comparative Example 2 Preparation of micro-nano zero-valent iron/carbon (Fe ⁰ /C) composite material

S1: Put 3.232g iron nitrate and 1.12g bagasse through a 60-mesh sieve into a beaker with 50mL deionized water. Place the beaker on a magnetic stirrer and stir for 2 hours at a speed of 500r/min. Then take out the solid matter and place it in the beaker. Dry at 65℃ for later use;

S2: Transfer the dried sample to a corundum ark, place it in a tube furnace, and raise the temperature from normal temperature to 600°C, 700°C, 800°C, and 900°C at 5°C/min for 180 minutes. The entire process is protected by nitrogen. After natural cooling, it was sieved to obtain micro-nano Fe ⁰ /C composite materials, which were recorded as Fe/CB@600, Fe/CB@700, Fe/CB@800 and Fe/CB@900 respectively.

Experimental Example 1 Microstructure Analysis and Characterization of Each Sample of Examples 1 and 2 and Comparative Examples 1 and 2

Figure 1 is an XRD pattern of micro-nano Fe ⁰ /C composite materials prepared by carbothermal reduction of different dosages of catalysts (auxiliaries) according to the present invention; as shown in the figure, Fe/CB _0.4 prepared in Reference Document 2 contains a variety of iron oxides . After adding 0.005 catalyst (agent), the crystallinity of the prepared material decreased, and the diffraction peak intensity of Fe ⁰ decreased significantly. This is considered to be that the addition of the catalyst (agent) promoted the melting of iron oxide, but due to the dosage The reason is that all iron oxides cannot be combined with the catalyst (auxiliary) and then recrystallized, resulting in a decrease in the crystallinity of the material. After adding 0.01 catalyst (agent), the diffraction peak of Fe ₃ O ₄ is strongly enhanced. This is because Fe ₃ O ₄ is the first substance generated after the oxidation of iron salt, and the catalyst (agent) first melts with it, improving the crystallinity. . When 0.02 of the catalyst (assistant) is added, the catalyst (assistant) can melt with most of the intermediate transition state iron oxides and promote the transformation of the intermediate transition state iron oxides into zero-valent iron during the carbothermal reduction process. After adding 0.04 of the catalyst (agent), the dosage of the catalyst (agent) can exactly promote the transformation of the intermediate transition state iron oxide into zero-valent iron during the carbothermal reduction process. At this time, there is only the diffraction peak of Fe ⁰ . When the dosage of the catalyst (agent) is greater than 0.04, the crystallinity of the material is reduced again due to the melt combination of the excess catalyst (agent) and ^Fe0 . The results show that an appropriate proportion of catalysts (auxiliaries) can reduce the formation of intermediate transition state iron oxides in the prepared materials, promote their conversion to Fe ⁰ , and generate more Fe ⁰ .

Figure 2 is the XRD pattern of micro-nano Fe ⁰ /C composite materials prepared by carbothermal reduction with or without catalyst (auxiliary) at different temperatures of the present invention; as shown in the figure, Fe/CB@600, Fe prepared in Comparative Document 2 /CB@700 and Fe/CB@800 contain a variety of iron-containing substances and have complex compositions. This may be because the zero-valent iron generated at 800°C is not completely transformed and is in an intermediate transition state with weak crystallinity. As the carbonization reduction temperature rises from 600°C to 900°C, the components of Fe/CB are gradually converted into zero-valent iron. The Fe/CB@900 spectrum shows the diffraction of Fe ₃ O ₄ and Fe ⁰ . peak, and the Fe ⁰ diffraction peak intensity in Fe/CB@900 is stronger than that of Fe/CB@600, Fe/CB@700, and Fe/CB@800. Among the material components of Fe/CB-Na@600, Fe/CB-Na@700, Fe/CB-Na@800 and Fe/CB-Na@900 in Example 2, there is only ^{one diffraction peak of Fe 0} . When the carbonization reduction temperature increases from 600℃ to 900℃, the Fe ⁰ diffraction peak intensity in Fe/CB-Na@900 is compared with that of Fe/CB-Na@600, Fe/CB-Na@700 and Fe/CB-Na@ The diffraction peak intensity of 800 is stronger. In addition, comparing Fe/CB@700 and Fe/CB-Na@700, it can be seen that the diffraction peak intensity of Fe/CB-Na@700 is stronger and there is only one diffraction peak of Fe ⁰ , achieving a significant reduction in carbothermal reduction preparation The pyrolysis temperature of zero-valent iron effectively increases the zero-valent iron content and reduces costs. The Fe ⁰ content of the micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction with or without catalyst (auxiliary) at different temperatures in Example 2 was measured in combination with the (GB T 6730.6-2016) method. The results are shown in Figure 3. Materials containing catalyst (assistant) sodium nitrate produce more Fe ⁰ during low-temperature preparation.

The micro-nano Fe ⁰ /C composite materials prepared at different carbothermal reduction temperatures in Example 2 were subjected to scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are shown in Figures 4-6 and 7 respectively. The micro-nano Fe ⁰ /C composite material is three-dimensional, with a large number of regular particles in the gaps between the materials, and the particle size decreases with the increase of the preparation temperature. There are a large number of holes and regular crystals related to Fe on the surface of micro-nano Fe ⁰ /C composite materials. After magnification, several regular octahedral crystals located on the surface of the micro-nano Fe ⁰ /C composite material or embedded in the holes can be observed. This shows the tight binding of Fe ⁰ and C, and high temperature can cause the active site to be highly rearranged. The average particle size of the crystals located on the surface is 366nm, and the crystals located inside are smaller, with an average particle size of 82nm. It can be seen from TEM that the Fe ⁰ particles dispersed inside the carbon package vary in size, and there are particles of Fe ⁰ agglomerates with a diameter of about 10.41-107.9 nm that are individually wrapped by the carbon carrier CB. High-resolution TEM shows obvious lattice stripes. The lattice spacing of the micro-nano Fe ⁰ /C composite is d=0.24nm, which corresponds to the (110) crystal plane. At the same time, SAED shows that Fe ⁰ has obvious (110) and (200) crystal planes, and the (211) crystal plane is vaguely visible. SEM and TEM results prove that Fe ⁰ in Fe ⁰ /CB material was successfully prepared and showed a certain dispersed form. The SEM results of the micro-nano Fe ⁰ /C composite material of Comparative Example 1 are shown in Figure 8. Zerovalent iron and ferric oxide are agglomerated, the reaction active sites are reduced, and the reducing ability of the catalyst is reduced.

Application example 1

1. Carbothermal reduction to prepare micro-nano Fe ⁰ /C composites and nano-zero-valent iron activated persulfate to remove antibiotics

To the solution contaminated with 80 mg/L metronidazole, 0.5 g/L of micro-nano Fe ⁰ /C composite material, nano-zero-valent iron (nZVI) or oxidized nano-zero-valent iron (O ₂ /nZVI) were added. Then add sodium peroxodisulfate (PDS) as an oxidant to the reaction system. The corresponding reaction conditions are: 80mg/L metronidazole, 0.5g/L material, 1mM PDS, room temperature, pH=6.7, shaker 250rpm, among which the nanometer zero-valent iron (nZVI) group needs to be stored in an atmosphere box. Samples were taken at each sampling time point, and the metronidazole concentration was detected and analyzed on a high-performance liquid chromatograph. The results are shown in Figure 9.

As can be seen from Figure 9, micro-nano Fe ⁰ /C composites and nano-zero-valent iron (nZVI)-activated persulfate have similar metronidazole removal efficiencies. The metronidazole activation efficiency and removal efficiency of oxidized nZVI are lower than those of nZVI stored in an atmosphere box, while the micro-nano Fe ⁰ /C composite material does not require atmosphere storage and has the same effect as nZVI stored in an atmosphere. This shows that the micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction has the same reactivity as nZVI, and the micro-nano Fe ⁰ /C composite material is more convenient to store, and the preparation and transportation costs are reduced.

2. Experimental method for removing metronidazole by activating sodium peroxodisulfate (PDS) using micro-nano Fe0/C composites prepared at different temperatures.

Micro-nano Fe ⁰ /C composite materials (with catalyst groups: Fe/CB-Na@600, Fe/CB-Na@) were prepared by adding 0.04g/L to the solution contaminated with 10mg/L metronidazole at different temperatures. 700, Fe/CB-Na@800, Fe/CB-Na@900; no catalyst group: Fe/CB@600, Fe/CB@700, Fe/CB@800 and Fe/CB@900) and blank experimental group CB material. Then add sodium peroxodisulfate (PDS) as an oxidant to the reaction system. The corresponding reaction conditions are: 10mg/L metronidazole, 0.04g/L different micro-nano Fe ⁰ /C composite materials, 1mM PDS, room temperature, pH=6.7, shaker 250rpm. Samples were taken at sampling time points, and the metronidazole concentration was detected and analyzed on a high-performance liquid chromatograph. The results are shown in Figure 10.

It can be seen from Figure 10 that the adsorption removal rate of metronidazole by the blank experimental group CB (bagasse carbon) material at different temperatures is below 35%. The removal efficiency of metronidazole of the micro-nano Fe ⁰ /C composite material prepared without the addition of a catalyst (agent) decreases significantly as the temperature decreases, while the micro-nano Fe ⁰ /C composite material prepared with a catalyst (agent) Under the preparation conditions of 700℃, the removal efficiency is still more than 90%. This proves that the catalyst (agent) can reduce the temperature of the carbothermal reduction reaction and prepare more zero-valent iron materials dispersed in the carbon carrier at low temperatures.

3. Experimental method for removing metronidazole by activating sodium peroxodisulfate (PDS) with micro-nano Fe ⁰ /C composite material

Add 0.04g/L Fe/CB-Na@700 to the solution contaminated with 10mg/L metronidazole. Then add sodium peroxodisulfate (PDS) as an oxidant to the reaction system. The corresponding reaction conditions are: 10mg/L metronidazole, 0.04g/L different micro-nano Fe ⁰ /C composite materials, 1mM PDS, room temperature, pH=6.7, shaker 250rpm. Samples were taken at each sampling time point, and the intermediate products of metronidazole degradation were detected and analyzed on a high-performance liquid chromatography-mass spectrometer. The results are shown in Figure 11.

It can be seen from Figure 11 that the micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction can activate PDS to remove metronidazole, and degrade metronidazole through free radical oxidation and non-free radical oxidation.

4. Experimental method for removing various organic pollutants by activating sodium peroxodisulfate (PDS) with micro-nano Fe ⁰ /C composite materials

Add 0.5g/L of different solutions containing 20mg/L norfloxacin, 20mg/L bromodiphenyl ether, 20mg/L florfenicol, 20mg/L oxytetracycline, and 20mg/L tetracycline. Micro-nano Fe ⁰ /C composite materials were prepared at high temperature. Then add sodium peroxodisulfate (PDS) as an oxidant to the reaction system. The corresponding reaction conditions are: 20mg/L pollutant, 0.5g/L micro-nano Fe ⁰ /C composite material, 1mM PDS, room temperature, pH=6.7, shaker 250rpm. Samples were taken at sampling time points, and the metronidazole concentration was detected and analyzed on a high-performance liquid chromatograph. The results are shown in Figure 12.

As can be seen from Figure 12, the micro-nano Fe ⁰ /C composite material prepared by carbothermal reduction can activate PDS to remove a variety of organic pollutants, including but not limited to metronidazole, norfloxacin, brominated diphenyl ether, fluorine Benicol, oxytetracycline, tetracycline and other organic pollutants.

Claims (10)

1. The micro-nano zero-valent iron/carbon composite material is characterized by comprising porous carbon and zero-valent iron particles distributed in or on the carbon material, wherein the diameter of the zero-valent iron particles is less than or equal to 0.5 mu m.

2. The micro-nano zero-valent iron/carbon composite of claim 1, wherein the zero-valent iron content of the micro-nano zero-valent iron/carbon composite is greater than 40%.

3. The preparation method of the micro-nano zero-valent iron/carbon composite material is characterized by comprising the following steps of: mixing ferric salt, biomass and a catalyst, and performing carbothermic reaction to obtain the micro-nano zero-valent iron/carbon composite material; the catalyst comprises at least one of sodium salt, potassium salt or cryolite.

4. The method of producing a micro-nano zero-valent iron/carbon composite of claim 3, wherein the biomass is at least one of straw, rice hulls, bagasse, coconut shells, distillers grains, wood chips, or bamboo chips.

5. The method of preparing a micro-nano zero-valent iron/carbon composite of claim 3, wherein the iron salt is selected from at least one of ferric nitrate, ferric chloride, or ferric carbonate.

6. The method of preparing a micro-nano zero-valent iron/carbon composite according to any one of claims 3 to 5, wherein the mass ratio of the iron salt to biomass is 10: (1-5);

and/or the mass ratio of the ferric salt to the catalyst is 10: (0.01-0.6).

7. The method for preparing a micro-nano zero-valent iron/carbon composite material according to claim 3, wherein the mixing mode is solution mixing or ball milling mixing;

and/or the solvent mixed by the solution is water.

8. A method of preparing a micro-nano zero-valent iron/carbon composite according to claim 3, wherein the carbothermal reaction conditions are selected from one or more of the following:

a) The temperature rising rate is 5-15 ℃/min;

b) The reaction temperature is 600-900 ℃;

c) The reaction time is 1-3 h.

9. A method of preparing a micro-nano zero-valent iron/carbon composite according to claim 3, wherein the carbothermal reaction is performed under a protective atmosphere.

10. Use of a micro-nano zero-valent iron/carbon composite material in the treatment of contaminated wastewater, characterized in that the micro-nano zero-valent iron/carbon composite material is a micro-nano zero-valent iron/carbon composite material according to any one of claims 1-2 or a micro-nano zero-valent iron/carbon composite material produced by the production method according to any one of claims 3-9.