Preparation and application of derived goethite electro-Fenton catalytic membrane

Abstract

The invention relates to the technical field of electro-Fenton catalytic membranes and organic polluted wastewater treatment, in particular to a preparation method and application of a derived goethite electro-Fenton catalytic membrane. An electro-Fenton catalyst with carbon nanotubes (CNTs) as a functional substrate is loaded on a polytetrafluoroethylene basement membrane, oxygen is subjected to an oxygen reduction reaction on the substrate CNTs to generate H2O2, the H2O2 and lattice iron (equivalent to Fe) in goethite alpha-FeO (OH) derived by a hydrothermal method form a'Fenton reagent ', and a Fenton reaction is further carried out to generate hydroxyl free radicals with strong oxidizing property. The prepared derivative goethite electro-Fenton catalytic membrane is stable in structure, alpha-FeO (OH) is not prone to falling off, iron ions are not prone to being leached out, the contact efficiency of pollutants and strong oxidizing free radicals is effectively improved in a circulation flow operation system, and efficient mineralization detoxification of the pollutants is achieved. The electro-Fenton catalytic membrane disclosed by the invention is simple in preparation process, and can realize energy-saving and efficient wastewater purification in the application of pollutant degradation.

Description

TECHNICAL FIELD

[0003] The application relates to the technical field of electro-catalysis, Fenton coupling membranes and organic wastewater treatment, and particularly relates to a preparation and application of an electro-Fenton catalytic membrane derived from goethite. BACKGROUND

[0005] Aromatic compounds are widely used as key precursors or intermediates in the synthesis of herbicides, fungicides, preservatives and other agricultural chemicals and industrial aids. They are difficult to biodegrade in water bodies due to their high chemical and thermal stability, and are listed as priority controlled toxic pollutants by the United States Environmental Protection Agency, and are also classified as potential human carcinogens by the World Health Organization and the International Cancer Research Agency, which seriously threatens human health. In recent years, the electro-Fenton (E-Fenton) technology has been widely used in the field of aromatic compound treatment due to its green and efficient characteristics.

[0006] The technology generates hydrogen peroxide (H2O2) in situ through the oxidation-reduction reaction of oxygen electrons, effectively avoiding the H2O2 dosing and transportation risks of traditional Fenton reaction, and reducing the use cost of H2O2. However, ferrous ions (Fe 2+ ) need to be added to generate strong oxidizing hydroxyl radicals (·OH) through Fenton reaction, but Fe 2+ is greatly affected by the pH of water bodies, is easy to form iron sludge, and the catalyst is difficult to recover, which is not conducive to repeated use. To this end, the iron source is fixed on the surface or inside of the catalyst to construct a heterogeneous E-Fenton catalyst, thereby reducing iron leaching and slowing down the production of iron sludge, and the catalyst can be reused.

[0007] The heterogeneous E-Fenton reaction benefits from the iron-functionalized cathode, and the selection of the iron source in the cathode preparation process is crucial. Since iron ore is abundant in nature and cheap and easy to obtain, it has more advantages and potential to be used as the iron source of the catalyst. In particular, goethite (Goethite, alpha-FeO(OH)) as one of the most stable oxidized irons in thermodynamics has a unique crystal structure and excellent reaction active site compared with tetragonal ferrihydrite (beta-FeO(OH)) and lepidocrocite (gamma-FeO(OH)), and also does not introduce harmful substances like pyrite (FeS2), thereby standing out as the iron source in the Fenton catalyst. However, the electrode material prepared by the natural goethite functionalized cathode is not stable, and alpha-FeO(OH) is easy to fall off, which is not conducive to recovery and reuse. Therefore, the combination of in-situ derived goethite and electrode material is more stable, and has more advantages in the heterogeneous E-Fenton catalyst for purifying wastewater.

[0008] In the traditional heterogeneous E-Fenton reaction, pollutant molecules need to reach the electrode surface to react with active free radicals (mainly ·OH). This results in a certain diffusion layer thickness between the pollutant and the electrode interface, limiting the degradation rate. This research focuses on developing membrane coupling technology to fabricate membrane electrodes, allowing water to pass through the electrodes under gravity or external forces. The passage of polluted water through the electrodes significantly improves the mass transfer rate between pollutants and the catalyst.

[0009] In E-Fenton cathode films, carbon nanotube films are favored as derivative functional substrates in the heterogeneous E-Fenton field due to their excellent conductivity, physicochemical properties, and large specific surface area. Furthermore, their abundant reactive sites facilitate oxygen reduction reactions to generate H₂O₂. To further optimize the treatment of aromatic compounds, a derivative goethite electro-Fenton catalytic membrane was prepared. Applying this electrocatalytic membrane to a circulating reactor overcomes mass transfer limitations while enhancing the contact oxidation efficiency between active species and pollutants, providing an economical and efficient scientific and technological approach for the mineralization and detoxification of aromatic compounds. Summary of the Invention

[0011] Therefore, the purpose of this invention is to provide a method for preparing and applying a derived goethite electro-Fenton catalytic membrane.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] This invention provides a goethite-derived electro-Fenton catalytic membrane, comprising a base membrane and an electrocatalytic active material, wherein the electrocatalytic active material is mainly carbon nanotubes with goethite (α-FeO(OH)) derived on its surface.

[0014] Preferably, the carbon nanotubes are 10-30 μm long, 5-20 nm in inner diameter, and 20-50 nm in outer diameter. The carbon nanotube content in the electrocatalytic active material is 100%, and the content of metal α-FeO(OH) accounts for 2-5% of the carbon nanotube content.

[0015] The present invention also provides a method for preparing the derived goethite electro-Fenton catalytic membrane described in the above technical solution, comprising the following steps:

[0016] Carbon nanotubes were pretreated by acidification, then washed and dried to serve as functional substrates derived from goethite in situ, denoted as ACNTs.

[0017] The ACNTs were ultrasonically dispersed in a precursor solution, and goethite was derived by a mild hydrothermal reaction. The resulting solid was washed and dried after the reaction and denoted as α-FeO(OH)@ACNTs.

[0018] A certain amount of the α-FeO(OH)@ACNTs was dispersed in an organic solvent to prepare a dispersion.

[0019] The dispersion was filtered through a substrate membrane and dried under vacuum to obtain a derived goethite electro-Fenton catalytic membrane, denoted as α-FeO(OH)@ACNTs / M.

[0020] Preferably, the acidification pretreatment solution comprises concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:(1~5); the ultrasonic dispersion time before acidification pretreatment is 30~60 min; the acidification pretreatment temperature is 60~120℃ and the acidification pretreatment time is 2~8 h; the washing is done with deionized water until the pH of the filtrate is 6~7.

[0021] Preferably, the solute composition of the precursor solution mainly includes ferric chloride hexahydrate and sodium sulfate, with a concentration ratio of 1:(0.5~3), and the solvent composition is deionized water, with a solute to solvent mass ratio of 1:(100~500); the amount of ACNTs added to the precursor solution is 50~100 mg, the ultrasonic dispersion time is 30~90 min; the hydrothermal reaction temperature is 100~140℃, and the reaction time is 4~8 h.

[0022] Preferably, the content of α-FeO(OH)@ACNTs added to the organic solvent is 10~40 mg by mass; the organic solvent is mainly N-methyl-pyrrolidone and anhydrous ethanol, with a volume of 20~60 mL and a dispersion time of 30~90 min.

[0023] Preferably, the ultrasonic dispersion frequency is 120~180 W.

[0024] Preferably, the drying process takes place in a vacuum environment at a temperature of 60-80°C.

[0025] Preferably, the base membrane is mainly a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane.

[0026] This invention also provides the application of the derived goethite electro-Fenton catalytic membrane described above in the electrocatalytic degradation of trace aromatic compounds in water in a continuous flow system.

[0027] Preferably, the flow rate in the continuous flow system is 1~5 mL / min, and the applied current density is 0.5~2.0 mA / cm². 2 .

[0028] Preferably, the aromatic compounds are mainly phenolic compounds such as phenol, 4-chlorophenol, 4-bromophenol, hydroquinone, and 2,4-dinitrophenol; the water contains the electrolyte sodium sulfate or sodium chloride.

[0029] The derivative goethite in the electrocatalytic active material of this invention has a simple preparation process and mild reaction conditions, which makes the binding of goethite more stable, slows down the shedding of active metal, and improves the stability of the electrocatalytic membrane.

[0030] The inherent properties of goethite derived in this invention make the iron reaction sites more stable, reduce iron ion leaching, slow down the formation of Fenton reaction iron sludge, reduce the cost of iron sludge treatment, and thus achieve a more economical water treatment solution.

[0031] The electrocatalytic active material of this invention uses carbon nanotubes as a functional substrate, which can promote electron migration and generate H2O2, a Fenton reagent, through a redox reaction with oxygen, thereby enhancing the generation of ·OH, which has strong oxidizing properties.

[0032] This invention selects polytetrafluoroethylene membrane or polyvinylidene fluoride membrane as the substrate membrane for electrocatalytic active material. The purpose is to achieve the fixation of electrocatalytic active material, overcome the problem of difficult recovery of E-Fenton catalyst in water treatment, and achieve the effect of repeated use of electrocatalytic active material.

[0033] This invention applies electrocatalytic membranes to continuous flow systems. The aim is to enable polluted water to pass through the membrane electrode assembly, achieving both sieving and catalytic degradation of pollutants. Simultaneously, passing through the membrane electrode assembly enhances the contact oxidation efficiency with active species generated from the electrocatalytic active material, overcoming the mass transfer limitations of traditional E-Fenton degradation systems. Attached Figure Description

[0035] Figure 1 The image shows a SEM image of α-FeO(OH)@ACNTs / M obtained in Example 1.

[0036] Figure 2 The XRD pattern of α-FeO(OH)@ACNTs / M obtained in Example 1;

[0037] Figure 3 The FT-IR spectrum of α-FeO(OH)@ACNTs / M prepared in Example 1;

[0038] Figure 4 This is a fine XPS spectrum of Fe 2p in α-FeO(OH)@ACNTs / M prepared in Example 1;

[0039] Figure 5 Tafel plots of the electrocatalytic membranes α-FeO(OH)@ACNTs / M, ACNTs / M, and α-FeO(OH) / M prepared in Example 1 and Comparative Example 1;

[0040] Figure 6The contact angle diagrams are shown for the electrocatalytic membranes α-FeO(OH)@ACNTs / M, ACNTs / M, and α-FeO(OH) / M prepared in Example 1 and Comparative Example 1.

[0041] Figure 7 The degradation results of the α-FeO(OH)@ACNTs / M electrocatalytic membrane obtained in Example 1 on simulated organic wastewater (pH 6-7) of 2,4-dinitrophenol and 4-chlorophenol in Flow-through operation mode are shown.

[0042] Figure 8 The degradation results of 4-chlorophenol simulated organic wastewater (pH about 3) by the α-FeO(OH)@ACNTs / M electrocatalytic membrane obtained in Example 1 under flow-by and flow-through operation modes are shown. Detailed implementation method:

[0043] This invention provides a goethite-derived electro-Fenton catalytic membrane, comprising a base membrane and an electrocatalytic active material, wherein the electrocatalytic active material is mainly carbon nanotubes with goethite (α-FeO(OH)) derived on its surface.

[0044] Preferably, the carbon nanotubes are 10-30 μm long, 5-20 nm in inner diameter, and 20-50 nm in outer diameter. The carbon nanotube content in the electrocatalytic active material is 100%, and the content of metal α-FeO(OH) accounts for 2-5% of the carbon nanotube content.

[0045] The present invention also provides a method for preparing the derived goethite electro-Fenton catalytic membrane described in the above technical solution, comprising the following steps:

[0046] Carbon nanotubes were pretreated by acidification, then washed and dried to serve as functional substrates derived from goethite in situ, denoted as ACNTs.

[0047] The ACNTs were ultrasonically dispersed in a precursor solution, and goethite was derived by a mild hydrothermal reaction. The resulting solid was washed and dried after the reaction and denoted as α-FeO(OH)@ACNTs.

[0048] A certain amount of the α-FeO(OH)@ACNTs was dispersed in an organic solvent to prepare a dispersion.

[0049] The dispersion was filtered through a substrate membrane and dried under vacuum to obtain a derived goethite electro-Fenton catalytic membrane, denoted as α-FeO(OH)@ACNTs / M.

[0050] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0051] This invention pretreats commercially available carbon nanotubes (CNTs) in a concentrated acid solution, sonicates them to fully disperse in the concentrated acid solution, heats them in a constant temperature oil bath, washes the acid solution with a large amount of deionized water until the filtrate is neutral, and then vacuum dries them to obtain goethite-derived substrate ACNTs.

[0052] In this invention, the acidification pretreatment solution comprises concentrated sulfuric acid and concentrated nitric acid, with a preferred volume ratio of 1:(1~5), more preferably 1:(2~3); the ultrasonic dispersion time before acidification pretreatment is preferably 30~90 min, more preferably 30~60 min; the acidification pretreatment temperature is preferably 60~120℃, more preferably 70~100℃, even more preferably 80℃; the acidification treatment time is preferably 2~8 h, more preferably 3~5 h; the washing is preferably done with deionized water, and the filtrate pH is preferably 6~7. In this invention, acidification pretreatment can increase the content of oxygen-containing functional groups on the surface of carbon nanotubes, providing more reactive sites for oxygen, thereby causing a redox reaction to produce H2O2.

[0053] In this invention, the precursor solution mainly comprises ferric chloride hexahydrate and sodium sulfate, with a concentration ratio preferably of 1:(0.5~3), more preferably 1:(1~2), and even more preferably 1:1; the solvent is deionized water, with a solute-to-solvent mass ratio of 1:(100~500), more preferably 1:(200~400), and even more preferably 1:(200~300); the amount of ACNTs added in the precursor solution is preferably 50~100 mg, more preferably 50~60 mg; the ultrasonic dispersion time is preferably 30~90 min, more preferably 30~60 min; the hydrothermal reaction temperature is preferably 100~140℃, more preferably 120~130℃, and even more preferably 120℃; the reaction time is preferably 4~8 h, more preferably 5~7 h, and even more preferably 6 h, resulting in α-FeO(OH)@ACNTs. In this invention, the proportion of sodium sulfate in the precursor, the hydrothermal reaction temperature, and the time affect the crystal structure of the derived goethite.

[0054] In this invention, the mass of α-FeO(OH)@ACNTs dispersed in an organic solvent is preferably 10-40 mg, more preferably 20-30 mg, and even more preferably 20 mg; the organic solvent is preferably N-methylpyrrolidone and anhydrous ethanol, and even more preferably N-methylpyrrolidone. In this invention, the volume of the organic solvent is preferably 20-60 mL, more preferably 30-40 mL, and the ultrasonic dispersion time is preferably 30-90 min, and even more preferably 60-90 min. In this invention, the organic solvent N-methylpyrrolidone, as a dispersant, enables a more stable bond between the electrocatalytic active material and the substrate membrane.

[0055] In this invention, the ultrasonic dispersion frequency is preferably 120~180 W, and more preferably 150~180 W.

[0056] In this invention, the vacuum drying temperature is preferably 60~80℃, more preferably 80℃, and the vacuum drying time is preferably 12~24 h.

[0057] In this invention, the base membrane is preferably a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane.

[0058] This invention also provides the application of the derived goethite electro-Fenton catalytic membrane described in the above technical solution or the derived goethite electro-Fenton catalytic membrane prepared by the preparation method described in the above technical solution in the electrocatalytic degradation of trace aromatic compounds in water in a continuous flow system.

[0059] In this invention, the flow rate in the continuous flow system is preferably 1~5 mL / min, more preferably 3~4 mL / min; the applied current density is preferably 0.5~2.0 mA / cm². 2 More preferably, it is 1.0~1.5 mA / cm 2 .

[0060] In this invention, the aromatic compound is preferably a phenolic compound such as phenol, 4-chlorophenol, 4-bromophenol, hydroquinone, or 2,4-dinitrophenol; the electrolyte in the water is preferably sodium sulfate or sodium chloride, more preferably sodium sulfate electrolyte, and its concentration is preferably 0.05 mol / L.

[0061] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes a derived goethite electro-Fenton catalytic membrane, its preparation method, and its application, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0062] Example 1

[0063] 300 mg of CNTs (10–30 μm in length, 10 nm in inner diameter, and 20 nm in outer diameter) were thoroughly dispersed in 150 mL of acidified pretreatment solution (V 浓硫酸 / V 浓硝酸 = 1 / 3), sonicated at 180 W for 60 min to ensure full contact between CNTs and concentrated acid solution. The mixture was then placed in a round-bottom flask and pretreated by heating and stirring at 80°C in an oil bath using a reflux condenser for 4 h. After acidification pretreatment, the mixture was cooled to room temperature, and CNTs were separated from the concentrated acid using a vacuum filtration device. The CNTs were then washed with a large amount of deionized water until the pH of the washing solution reached 6-7. The CNT powder was collected and dried in a vacuum drying oven at 80°C for 12 h, ground, and stored for later use, denoted as ACNTs.

[0064] 162.2 mg of ferric chloride hexahydrate (10 mmol / L) and 85.2 mg of sodium sulfate (10 mmol / L) were weighed and ultrasonically dispersed for 30 min to dissolve in 60 mL of deionized water to prepare a precursor solution. Then, 50 mg of ACNTs were added to the precursor solution, and the mixture was ultrasonically dispersed at 180 W for 1 h. The resulting reaction solution was transferred to a 100 mL high-pressure reactor and reacted at 120 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature, the solid was collected, and washed with 120 mL of deionized water. The resulting solid was dried in a vacuum drying oven at 80 °C for 12 h. The product was ground and stored for later use, denoted as α-FeO(OH)@ACNTs.

[0065] Weigh 20 mg of α-FeO(OH)@ACNTs and place them in 30 mL of N-methyl-pyrrolidone solvent. Disperse thoroughly under ultrasonication at 180 W for 1 h. Filter the dispersion onto the surface of a 5 μm pore size polytetrafluoroethylene membrane (hydrophilic) and vacuum dry for 12 h to obtain the α-FeO(OH)@ACNTs / M catalytic membrane.

[0066] Comparative Example 1

[0067] 300 mg of CNTs (10–30 μm in length, 10 nm in inner diameter, and 20 nm in outer diameter) were thoroughly dispersed in 150 mL of acidified pretreatment solution (V 浓硫酸 / V 浓硝酸= 1 / 3), sonicated at 180 W for 60 min to ensure full contact between CNTs and concentrated acid solution. The mixture was then placed in a round-bottom flask and pretreated by heating and stirring at 80°C in an oil bath using a reflux condenser for 4 h. After acidification pretreatment, the mixture was cooled to room temperature, and CNTs were separated from the concentrated acid using a vacuum filtration device. The CNTs were then washed with a large amount of deionized water until the pH of the washing solution reached 6-7. The CNT powder was collected and dried in a vacuum drying oven at 80°C for 12 h, ground, and stored for later use, denoted as ACNTs.

[0068] 162.2 mg of ferric chloride hexahydrate (10 mmol / L) and 85.2 mg of sodium sulfate (10 mmol / L) were weighed and ultrasonically dispersed for 30 min to dissolve in 60 mL of deionized water to prepare a precursor solution. The precursor solution was transferred to a 100 mL high-pressure reactor and reacted at 120 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, the solid was collected, and washed with 120 mL of deionized water. The resulting solid was dried in a vacuum drying oven at 80 °C for 12 h. The product was ground and stored for later use, and denoted as α-FeO(OH).

[0069] Weigh 20 mg of ACNTs and α-FeO(OH) and place them in 30 mL of N-methyl-pyrrolidone solvent, respectively, and disperse them thoroughly under ultrasonication at 180 W for 1 h. Filter the dispersions onto the surface of a 5 μm pore size polytetrafluoroethylene membrane (hydrophilic) and vacuum dry for 12 h. These are designated as ACNTs / M and α-FeO(OH) / M catalytic membranes, respectively.

[0070] Characterization and performance testing

[0071] Test Example 1

[0072] Figure 1 This is a SEM image of α-FeO(OH)@ACNTs / M prepared in Example 1. Figure 1 It can be seen that the smooth tubular outer wall of the prepared electrocatalytic membrane contains needle-like substances, which are derived goethite.

[0073] Figure 2 The XRD pattern of α-FeO(OH)@ACNTs / M prepared in Example 1 is shown below. Figure 2 It can be seen that the crystal structure of α-FeO(OH) in the prepared electrocatalytic membrane corresponds to that of the standard card, confirming that it is a derived goethite; ACNTs are mainly graphitic carbon structures.

[0074] Figure 3 The FT-IR spectrum of α-FeO(OH)@ACNTs / M prepared in Example 1 is shown below. Figure 3 It can be seen that the values ​​at 606, 792, and 885 cm are... -1The peak at this point represents the characteristic Fe-O diffraction peak in α-FeO(OH) derived from ACNTs.

[0075] Figure 4 This is the fine XPS spectrum of Fe 2p in α-FeO(OH)@ACNTs / M prepared in Example 1, obtained by... Figure 4 It can be seen that the α-FeO(OH) derived from ACNTs is mainly Fe(Ⅲ).

[0076] Figure 5 The above are Tafel plots of the electrocatalytic membranes α-FeO(OH)@ACNTs / M, ACNTs / M, and α-FeO(OH) / M prepared in Example 1 and Comparative Example 1, from... Figure 5 It can be seen that the prepared α-FeO(OH)@ACNTs / M has good corrosion resistance, and the derivatization of α-FeO(OH) in ACNTs can enhance the corrosion resistance of ACNTs / M.

[0077] Figure 6 The contact angle diagrams are for the electrocatalytic membranes α-FeO(OH)@ACNTs / M, ACNTs / M, and α-FeO(OH) / M prepared in Example 1 and Comparative Example 1. Figure 6 It can be seen that the α-FeO(OH)@ACNTs / M membrane prepared by deriving α-FeO(OH) in ACNTs has good hydrophilicity, which is beneficial to enhance the water flux of the electrocatalytic membrane and improve the contact oxidation efficiency of pollutants and electrocatalytic active materials.

[0078] Test Example 2

[0079] Simulated organic wastewaters of 4-chlorophenol and 2,4-dinitrophenol were prepared separately, with a concentration of 10 mg / L and a pH of 6-7. Both simulated organic wastewaters contained 0.05 mol / L Na2SO4 as an electrolyte. The two simulated organic wastewaters were then used for degradation experiments.

[0080] The electrocatalytic membrane prepared in Example 1 was used as the cathode, and a platinum mesh as the anode, to degrade organic wastewater in a flow-through operation mode. The flow-through operation mode was constructed as follows: the cathode and anode were placed opposite each other, with the anode positioned above the cathode (effective reaction membrane surface facing upwards) and parallel to the horizontal plane, in a flow-through reactor. A peristaltic pump was used to apply pressure to the organic wastewater, causing it to pass vertically through the membrane electrodes sequentially. The degraded wastewater circulated through the reactor, and the peristaltic pump was set to a circulation flow rate of 3 mL / min. The electrode spacing was set to 4 mm, the reactor volume to approximately 2 mL, and the effective reaction area of ​​the electrocatalytic membrane to be 3.14 cm². 2An aeration device was installed in the simulated organic wastewater, with an aeration rate of approximately 200 mL / min, and a constant current density of 1.0 mA / cm² was applied. 2 A degradation experiment was conducted, simulating the degradation of 30 mL of organic wastewater.

[0081] During the experiments with two types of organic wastewater, at different degradation times, 1 mL of simulated organic wastewater solution was taken to test the concentration of 4-chlorophenol or 2,4-dinitrophenol. The degradation effect of the electrocatalytic membrane on the two organic pollutants was as follows: Figure 7 See Table 1.

[0082] Table 1. Degradation effect of the α-FeO(OH)@ACNTs / M membrane obtained in Example 1 on 4-chlorophenol and 2,4-dinitrophenol.

[0083] Different degrading pollutants 120 min degradation efficiency (%) Degradation reaction rate constant k app (min -1 )]]> 4-chlorophenol 88.83 0.0162 2,4-dinitrophenol 71.04 0.0097

[0084] Table 1 shows that the electrocatalytic membrane α-FeO(OH)@ACNTs / M achieved a degradation rate of 88.83% for 4-chlorophenol and 71.04% for 2,4-dinitrophenol within 120 min, confirming that the α-FeO(OH)@ACNTs / M electrocatalytic membrane has a good degradation effect on phenolic compounds.

[0085] Test Example 3

[0086] A simulated organic wastewater containing 4-chlorophenol was prepared at a concentration of 10 mg / L. The simulated organic wastewater also contained 0.05 mol / L Na2SO4 as an electrolyte. The pH of the solution was adjusted to approximately 3 using 1 mol / L H2SO4 to make the simulated organic wastewater closer to the actual pH environment of the water body, which is also the optimal pH environment for the Fenton reaction, and was used for degradation experiments.

[0087] The electrocatalytic membrane prepared in Example 1 was used as the cathode, and a platinum mesh as the anode. The degradation effect of the electrocatalytic membrane on 4-chlorophenol was compared in flow-by and flow-through operating modes. Flow-by operating mode construction: The cathode and anode were fixed in the electrolytic cell using electrode clamps. The effective reaction surface of the cathode membrane was placed opposite the anode and perpendicular to the horizontal plane. The distance between the two electrodes was set to 4 mm, and the effective reaction area of ​​the electrocatalytic membrane was approximately 6.25 cm². 2Flow-through operation mode setup: The anode is positioned above the cathode (effective reaction membrane surface facing upwards) and parallel to the horizontal plane in a flow-through reactor. A peristaltic pump applies pressure to the organic wastewater, causing it to pass vertically through the membrane electrodes sequentially. The degraded wastewater circulates through the reactor, with the peristaltic pump setting the circulation rate to 4 mL / min. The electrode spacing is 4 mm, the reactor volume is approximately 2 mL, and the effective reaction area of ​​the electrocatalytic membrane is 3.14 cm². 2 In both modes, an aeration device was installed with an aeration rate of approximately 200 mL / min, and a constant current density of 1.0 mA / cm² was applied. 2 Degradation experiments were conducted, with each simulated organic wastewater volume being 30 mL.

[0088] During the experiment, at different degradation times, 1 mL of simulated organic wastewater was taken to test the concentration of 4-chlorophenol. The degradation effects of flow-by and flow-through modes were as follows: Figure 8 And Table 2.

[0089] Table 2. Degradation effect of α-FeO(OH)@ACNTs / M membrane obtained in Example 1 on 4-chlorophenol in flow-by and flow-through modes.

[0090] Degradation conditions 30 min degradation efficiency (%) Degradation reaction rate constant k app (min -1 )]]> Flow-by 61.94 0.0310 Flow-through 97.82 0.1292

[0091] Table 2 shows that, given that the effective reaction area in the flow-through mode is half that in the flow-by mode, the α-FeO(OH)@ACNTs / M catalytic membrane exhibits significantly higher degradation efficiency for 4-chlorophenol in the flow-through mode than in the flow-by mode, reaching 97.82%, compared to only 61.93% in the flow-by mode. Furthermore, the degradation kinetics of 4-chlorophenol in the flow-through mode are much higher than those in the flow-by mode, indicating that the α-FeO(OH)@ACNTs / M catalytic membrane achieves higher efficiency in degrading phenolic compounds via the electro-Fenton reaction in the flow-through mode.

[0092] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A derivative goethite electro-Fenton catalytic membrane, characterized in that, It includes a base membrane and an electrocatalytic active material, the electrocatalytic active material being mainly carbon nanotubes with goethite (α-FeO(OH)) derived on their surface.

2. The derived goethite electro-Fenton catalytic membrane according to claim 1, characterized in that, The carbon nanotubes are 10-30 μm long, 5-20 nm in inner diameter, and 20-50 nm in outer diameter. The carbon nanotube content in the electrocatalytic active material is 100%, and the content of metal α-FeO(OH) accounts for 2-5% of the carbon nanotube content.

3. A method for preparing an electro-Fenton catalytic membrane, characterized in that, The preparation method steps are as follows: Carbon nanotubes were pretreated by acidification, then washed and dried to serve as functional substrates derived from goethite in situ, denoted as ACNTs. The ACNTs were ultrasonically dispersed in a precursor solution, and goethite was derived by a mild hydrothermal reaction. The resulting solid was washed and dried after the reaction and denoted as α-FeO(OH)@ACNTs. A certain amount of the α-FeO(OH)@ACNTs was dispersed in an organic solvent to prepare a dispersion. The dispersion was filtered through a substrate membrane and dried under vacuum to obtain a derived goethite electro-Fenton catalytic membrane, denoted as α-FeO(OH)@ACNTs / M.

4. The preparation method according to claim 3, characterized in that, The acidification pretreatment solution includes concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:(1~5), which are ultrasonically dispersed and then heated in a constant temperature oil bath. The acidification pretreatment temperature is 60~120℃ and the acidification pretreatment time is 2~8 h. The ultrasonic dispersion time is 30~90 min and the frequency is 120~180 W. The washing is done with deionized water until the pH of the filtrate is 6~7.

5. The preparation method according to claim 3, characterized in that, The solute composition of the precursor solution mainly includes ferric chloride hexahydrate and sodium sulfate, with a concentration ratio of 1:(0.5~3), and the solvent composition is deionized water, with a solute to solvent mass ratio of 1:(100~500); the amount of ACNTs added to the precursor solution is 50~100 mg, and the ultrasonic dispersion time is 30~90 min; the hydrothermal reaction temperature is 100~140℃, and the reaction time is 4~8 h.

6. The preparation method according to claim 3, characterized in that, The α-FeO(OH)@ACNTs added to the organic solvent are 10-40 mg by mass; the organic solvent is mainly N-methyl-pyrrolidone and anhydrous ethanol, with a volume of 30-60 mL and a dispersion time of 30-90 min.

7. The preparation method according to claim 3, characterized in that, The drying process takes place in a vacuum environment, with the temperature mainly between 60 and 80°C.

8. The preparation method according to claim 3, characterized in that, The base membrane is mainly a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane.

9. The application of the derived goethite electro-Fenton catalytic membrane as described in claim 1 or 2 in the electrocatalytic degradation of trace aromatic compounds in water in a continuous flow system, characterized in that... The continuous flow rate is 1–5 mL / min, and the applied current density is 0.5–2.0 mA / cm². 2 .

10. The application according to claim 9, characterized in that, The aromatic compounds are mainly phenolic compounds such as phenol, 4-chlorophenol, 4-bromophenol, hydroquinone, and 2,4-dinitrophenol, and the water contains the electrolyte sodium sulfate or sodium chloride.

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