A Fe-GC@Fe 0 Catalysts, their preparation methods and applications

Abstract

This invention discloses a Fe-GC@Fe 0 This invention relates to catalysts, their preparation methods, and applications, belonging to the field of water treatment technology. The preparation method of this invention is simple, requires minimal equipment, and yields Fe-GC@Fe catalysts. 0 The catalyst can drive microorganisms in water to metabolize perfluorinated compounds. Under conditions without external energy input, it can effectively remove perfluorinated compounds such as perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorononanoic acid, and perfluorohexane sulfonic acid from water. The removal rate and defluorination rate both reach more than 80%. Moreover, it is a solid catalyst, which is easy to separate from water, recycle and reuse, and maintain a high removal effect.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a Fe-GC@Fe 0 Catalysts, their preparation methods, and applications. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental pollutants with over 12,000 unique known structures, including perfluorooctanoic acid, perfluorononanoic acid, perfluorooctane sulfonic acid, and perfluorohexane sulfonic acid. The widespread use of PFAS in over 200 sectors means they are inevitably present in surface water, municipal wastewater, and even drinking water. Numerous studies have shown that even trace amounts of PFAS pose serious risks to human health and the environment due to their high toxicity, persistence, and bioaccumulation potential.

[0003] Currently, methods for removing PFAS include thermal treatment, electrochemical methods, ultrasonic methods, advanced oxidation methods, and ultraviolet oxidation methods. However, these methods require the assistance of external energy sources such as oxidants or reducing agents, light, electricity, heat, and ultrasound to mineralize PFAS. Furthermore, the presence of dissolved organic carbon and coexisting anions in water can significantly inhibit the destruction of PFAS. Developing a cost-effective PFAS mineralization technology remains an urgent scientific challenge.

[0004] Based on this, a Fe-GC@Fe method for PFAS mineralization without the need for additional auxiliary energy sources and reagents is proposed. 0 Catalysts and their preparation methods. Summary of the Invention

[0005] The purpose of this invention is to provide a Fe-GC@Fe 0 Catalysts, their preparation methods, and applications are described to address the problems in the background art.

[0006] To achieve the above objectives, the present invention provides a Fe-GC@Fe 0 The catalyst and its preparation method include the following steps:

[0007] S1. Dissolve ferric nitrate nonahydrate and dimethylimidazole in deionized water to form solution A, and dissolve ferric nitrate nonahydrate and trimesic acid in deionized water to form solution B.

[0008] S2. Mix solution A and solution B thoroughly and dry them to obtain solid C.

[0009] S3. Dissolve solid C, carbon source, and nitrogen source in deionized water, stir and mix well, and dry to obtain solid D;

[0010] S4. Solid D is placed in a porcelain boat and calcined in a tube furnace under nitrogen atmosphere. After calcination, it is ground into powder to obtain Fe-GC@Fe. 0 catalyst.

[0011] Preferably, in S1, the amount of ferric nitrate nonahydrate is 8-13 mmol, the amount of dimethylimidazole is 35-52 mmol, and the amount of trimesic acid is 5-14 mmol.

[0012] Preferably, in step S2, the stirring time is 2-4 hours, the drying temperature is 80-100°C, and the drying time is 24-36 hours.

[0013] Preferably, in S3, the mass of solid C is 100~300mg, the mass of carbon source is 3~6g, and the mass of nitrogen source is 1~3g.

[0014] Preferably, in S3, the carbon source is one or more of mannitol, ascorbic acid, citric acid and polyethylene glycol, and the nitrogen source is one or more of melamine, dicyandiamine, 2-methylimidazole and urea.

[0015] Preferably, in step S4, the heating rate of the tubular furnace is 5~10℃ / min, the calcination temperature is 700~800℃, and the calcination time is 2~4h.

[0016] This invention also provides Fe-GC@Fe 0 Catalyst, the Fe-GC@Fe 0 The catalyst was prepared by the above method, Fe-GC@Fe 0 The catalyst is a black solid powder with a microstructure of sheet-like porous material; Fe-GC@Fe 0 The catalyst is composed of graphene-like carbon, zero-valent iron, Fe3O4, and Fe3C. The zero-valent iron is tightly coated by iron-complexed graphene-like carbon, which makes the catalytic performance more stable and less likely to dissolve in water.

[0017] Preferably, Fe-GC@Fe 0 The catalyst has a large specific surface area and numerous pores, which easily expose more reactive sites, promoting interfacial contact with PFAS molecules and microorganisms, enhancing the extracellular electron transfer process, and achieving rapid degradation of PFAS.

[0018] The present invention also provides the above-mentioned Fe-GC@Fe 0 The application of catalysts, namely Fe-GC@Fe 0 Catalysts are used in the removal of perfluorinated compounds from water.

[0019] Preferably, in the process of removing perfluorinated compounds from the water, Fe-GC@Fe 0A catalyst is used as a packing material to construct an upflow biofilter reactor. Municipal wastewater containing dissolved perfluorinated compounds is pumped into the reactor for perfluorinated compound removal. The water flow direction is bottom inlet and top outlet.

[0020] Preferably, the perfluorinated compound includes one or more of perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorononanoic acid, and perfluorohexane sulfonic acid.

[0021] Therefore, the present invention provides a Fe-GC@Fe 0 The catalyst, its preparation method, and its application have the following beneficial effects:

[0022] (1) This invention drives microorganisms in water by constructing a sufficiently strong electric field on the catalyst surface, and metabolizes PFAS through the extracellular electron transfer of microorganisms, thereby achieving defluorination, cracking and mineralization of PFAS under mild conditions. No external oxidant or reducing agent is required, and no external energy is needed to treat PFAS in wastewater with low energy consumption and high efficiency, which significantly reduces the cost of PFAS wastewater treatment.

[0023] (2) In the catalyst prepared by the present invention, zero-valent iron is coated in a graphene-like framework, which mainly plays the role of regulating the internal electron distribution of the material; the zero-valent iron, as an active center, does not react directly with PFAS, and the iron is non-consumable and has low dissolution; the catalyst material has a large specific surface area and many pores, which is conducive to the interfacial contact between the catalyst and PFAS molecules and microorganisms, and enhances the extracellular electron transfer process; the catalyst is a solid catalyst, which is easy to separate from water, recycle and reuse, and maintain a high removal effect.

[0024] (3) The preparation method of the present invention is simple and requires low equipment. The catalyst prepared by it can drive microorganisms in water to metabolize perfluorinated compounds. Under the condition of no external energy input, it can quickly and effectively remove perfluorinated compounds such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA) and perfluorohexane sulfonic acid (PFHxS) in water. After the microbial film is stabilized, the removal rate of PFAS and the defluorination rate of the system are both above 80%. Moreover, the iron element contained in the catalyst is a strong affinity element for microorganisms, which can promote the metabolic growth of microorganisms and make the biofilm on the surface of the material more stable.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 The XRD pattern of the catalyst in Example 1 of this invention;

[0027] Figure 2 These are SEM images of the catalyst in Example 1 of the present invention at different magnifications, where a is 200 nm and b is 1 μm;

[0028] Figure 3 This is a transmission electron microscope image of the catalyst in Example 1 of the present invention;

[0029] Figure 4 This is a transmission electron microscopy (TEM) elemental scan of the catalyst in Example 1 of this invention;

[0030] Figure 5 The image shows the HRTEM image of the catalyst in Example 1 of this invention.

[0031] Figure 6 The graph shows the degradation and defluorination rate of perfluorinated compounds by the catalyst in the application examples of this invention, where a is the perfluorinated compound removal rate and b is the defluorination rate. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0034] Example 1

[0035] This embodiment prepares a Fe-GC@Fe 0 The catalyst, and the specific steps are as follows:

[0036] S1. Dissolve 4g of ferric nitrate nonahydrate and 4g of dimethylimidazole in 60mL of deionized water to form solution A, and dissolve 4g of ferric nitrate nonahydrate and 4g of trimesic acid in 60mL of deionized water to form solution B.

[0037] S2. Mix solution A and solution B thoroughly for 3 hours, then dry them in an oven at 100°C for 24 hours to obtain solid C.

[0038] S3. Dissolve 200 mg of solid C, 5 g of polyethylene glycol as a carbon source, and 2 g of melamine as a nitrogen source in 300 mL of deionized water, stir and mix well, and dry in an oven at 100 °C to obtain solid D.

[0039] S4. Place solid D in a porcelain boat, and heat it to 800℃ at a rate of 10℃ / min using a tube furnace under nitrogen purging. Calcinate for 4 hours, then grind into powder to obtain Fe-GC@Fe. 0 catalyst.

[0040] The Fe-GC@Fe prepared in Example 1 0 Catalysts were characterized, such as Figure 1-5 As shown, from Figure 1 The XRD pattern of Fe-GC@Fe was compared with that of the standard card, revealing that... 0 The phase composition of the catalyst includes graphene-like carbon and Fe. 0 Fe3O4 and Fe3C. From Figure 2 The scanning electron microscope image shows that it is a porous material. Figure 3 The transmission electron microscopy image shows that black zero-valent iron particles are uniformly dispersed on graphene-like carbon. Figure 4 Elemental analysis revealed that the catalyst is composed of C, N, O, and Fe. Figure 5 This indicates that the catalyst contains Fe. 0 The presence of Fe2N and graphene-like carbon indicates the structure of the catalyst with iron-encapsulated graphene-like carbon encapsulating zero-valent iron.

[0041] Example 2

[0042] The preparation steps in this embodiment are the same as those in Example 1, except that mannitol is used as the carbon source, with an amount of 6g; dicyandiamine is used as the nitrogen source, with an amount of 3g; and solid C is 300mg.

[0043] Example 3

[0044] The preparation steps in this embodiment are the same as those in Example 1, except that citric acid is used as the carbon source, with an amount of 3g; 2-methylimidazole is used as the nitrogen source, with an amount of 1g; and solid C is 100mg.

[0045] Application Examples

[0046] The Fe-GC@Fe from Example 1 0 The catalyst is used to degrade the removal of perfluorinated compounds in water, specifically including the following steps:

[0047] 13.3g of the Fe-GC@Fe prepared in Example 1 was used. 0 The catalyst is packed in the reaction column to construct an upflow biological filter reactor; then, PFAS wastewater is pumped into the reactor by a peristaltic pump, with the water flow direction being bottom in and top out, and the retention time being 30 minutes.

[0048] The above-described method was used to conduct a continuous degradation experiment on perfluorinated compounds in water. The results of the perfluorinated compound removal rate are as follows: Figure 6 As shown, the results indicate that after the biofilm stabilizes, the catalyst achieves a PFAS removal rate and a defluorination rate of over 80%.

[0049] Therefore, the present invention provides a Fe-GC@Fe 0 Catalysts, their preparation methods and applications, and the Fe-GC@Fe catalysts prepared. 0The catalyst material has a large specific surface area and many pores, which is conducive to the interfacial contact between the catalyst and PFAS molecules and microorganisms, and enhances the extracellular electron transfer process. It can effectively and rapidly remove perfluorinated compounds such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) from water. After the microbial film is stabilized, the removal rate of PFAS and the defluorination rate of the system are both above 80%. Moreover, the iron element contained in the catalyst is a strong affinity element for microorganisms, which can promote the metabolic growth of microorganisms and make the biofilm on the surface of the material more stable.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A Fe-GC@Fe 0 A method for preparing a catalyst, characterized in that, Includes the following steps: S1. Dissolve ferric nitrate nonahydrate and dimethylimidazole in deionized water to form solution A, and dissolve ferric nitrate nonahydrate and trimesic acid in deionized water to form solution B. S2. Mix solution A and solution B thoroughly and dry them to obtain solid C. S3. Dissolve solid C, carbon source, and nitrogen source in deionized water, stir and mix well, and dry to obtain solid D. The carbon source is one or more of mannitol, ascorbic acid, citric acid, and polyethylene glycol, and the nitrogen source is one or more of melamine, dicyandiamine, 2-methylimidazole, and urea. S4. Solid D is placed in a porcelain boat and calcined in a tube furnace under nitrogen atmosphere. After calcination, it is ground into powder to obtain Fe-GC@Fe. 0 The catalyst is heated at a rate of 5-10℃ / min in a tubular furnace, calcined at a temperature of 700-800℃, and calcined for 2-4 hours.

2. The Fe-GC@Fe according to claim 1 0 A method for preparing a catalyst, characterized in that: In S1, the amount of ferric nitrate nonahydrate is 8-13 mmol, the amount of dimethylimidazole is 35-52 mmol, and the amount of trimesic acid is 5-14 mmol.

3. The Fe-GC@Fe according to claim 1 0 A method for preparing a catalyst, characterized in that: In step S2, the stirring time is 2-4 hours, the drying temperature is 80-100℃, and the drying time is 24-36 hours.

4. The Fe-GC@Fe according to claim 1 0 A method for preparing a catalyst, characterized in that: In S3, the mass of solid C is 100~300mg, the mass of carbon source is 3~6g, and the mass of nitrogen source is 1~3g.

5. A Fe-GC@Fe 0 The catalyst is characterized by: The Fe-GC@Fe 0 The catalyst is prepared by the preparation method according to any one of claims 1-4, Fe-GC@Fe 0 The catalyst is a black solid powder with a microstructure of sheet-like porous material; Fe-GC@Fe 0 The catalyst has a structure consisting of graphene-like carbon, zero-valent iron, Fe3O4, and Fe3C, wherein the zero-valent iron is tightly coated with iron-complexed graphene-like carbon.

6. The Fe-GC@Fe as described in claim 5 0 The application of catalysts is characterized by: The Fe-GC@Fe 0 Catalysts are used in the removal of perfluorinated compounds from water.

7. The Fe-GC@Fe according to claim 6 0 The application of catalysts is characterized by: During the removal of perfluorinated compounds from water, Fe-GC@Fe 0 A catalyst is used as a packing material to construct an upflow biofilter reactor. Municipal wastewater containing dissolved perfluorinated compounds is pumped into the reactor for perfluorinated compound removal.

8. The Fe-GC@Fe according to claim 7 0 The application of catalysts is characterized by: The perfluorinated compounds include one or more of perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorononanoic acid, and perfluorohexane sulfonic acid.

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