CN107601624B - Preparation and application of electro-Fenton cathode material based on supported activated carbon fibers - Google Patents

Abstract

The invention discloses the preparation and application of an electro-Fenton cathode material based on loaded activated carbon fibers. Dissolved oxygen generates hydrogen peroxide through a two-electron oxygen reduction reaction on the cathode surface of the activated carbon fibers, and the generated hydrogen peroxide and activated carbon fibers The surface-supported iron ion or copper ion complex catalyst reacts to generate strong oxidant hydroxyl radicals, which can oxidatively remove refractory organics under neutral pH conditions. The activated carbon fiber electro-Fenton cathode has a simple preparation method, mild conditions, and in-situ generation of hydrogen peroxide to avoid possible dangers during transportation and storage. Sludge production, no secondary pollution. The raw materials of the invention are cheap and easy to obtain, the preparation method is simple, the treatment period is short, and it is easy to combine with other treatment methods, and is favorable for large-scale production and comprehensive treatment of organic pollutants.

Description

Preparation and application of an electro-Fenton cathode material based on supported activated carbon fibers

technical field

The invention belongs to the technical field of environmental functional materials and electrochemical water treatment, and relates to a heterogeneous electro-Fenton activated carbon fiber cathode, in particular to the preparation and application of an electro-Fenton cathode material based on loaded activated carbon fibers.

Background technique

With economic development and social progress, a wide variety of pharmaceuticals and personal care products (PPCPs), including prescription and non-prescription drugs, veterinary medicines, cosmetics, synthetic musk, hair dyes and fungicides, are discharged into the water environment. This new type of pollution These substances are often prone to bioaccumulation, affecting aquatic organisms at low concentrations and, in turn, human health. Most of the PPCPs are discharged into the sewage in the raw or transformed form and enter the sewage treatment plant. At present, for this kind of sewage containing trace amount of refractory pollutants, there is no widely popularized economical and effective method at home and abroad. As an environmentally friendly advanced oxidation technology for water treatment, electro-Fenton process has attracted more and more attention in the treatment of refractory organic pollutants. Because it can generate H ₂ O ₂ in situ, it can effectively avoid the danger in transportation and storage. The traditional homogeneous electro-Fenton technology has strict pH requirements and is currently only suitable for the treatment of acidic wastewater (pH=2~4). For neutral and alkaline wastewater, a large amount of acid, Alkaline agents greatly increase the treatment cost, and a large amount of iron-containing sludge will be produced after the reaction, causing secondary pollution.

Due to the above limitations of the homogeneous electro-Fenton system, the research and development of heterogeneous electro-Fenton catalysts has always been the focus of research at home and abroad. Patent CN 105905985 A uses decontaminated graphite felt material as cathode, platinum wire as anode, saturated calomel electrode as reference electrode, graphene oxide suspension, 3-4-ethylenedioxythiophene and sodium poly-p-styrenesulfonate The mixed solution is the electrolyte, and the modified graphite felt heterogeneous electro-Fenton electrode is prepared by the cyclic voltammetry electropolymerization method; the patent CN103496764 A uses the high oxygen evolution overpotential electrode as the anode, the air diffusion electrode as the cathode, and the polytetrafluoroethylene is modified. The PTFE-bonded air diffusion electrode here is still to be investigated in terms of pressure resistance and scale-up experiments.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a preparation and application of an electro-Fenton cathode material based on supported activated carbon fibers, using the supported activated carbon fibers as a cathode, under neutral pH conditions, using Dissolved oxygen in water is electrochemically and rapidly reduced on the cathode surface to generate hydrogen peroxide in situ. Hydrogen peroxide reacts with iron ions or copper ion complexes supported on the carbon cathode surface to generate hydroxyl radicals, and oxidatively degrade organic compounds such as ibuprofen. pollutants.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A preparation of an electro-Fenton cathode material based on supported activated carbon fibers, comprising the following steps:

(1) take activated carbon fiber cathode base material for pretreatment;

(2) getting the pretreated material and immersing it in the complexing agent and the metal salt solution in turn;

(3) Rinse and dry for use.

The activated carbon fiber cathode base material is viscose-based activated carbon fiber, phenolic-based activated carbon fiber, pitch-based activated carbon fiber or polyacrylonitrile-based activated carbon fiber.

The pretreatment is to ultrasonically soak in acetone or absolute ethanol for 10-30 minutes, then ultrasonically soak in 1-3mol/L nitric acid solution for 10-30 minutes after cleaning, and finally rinse with deionized water, then dry for use.

The complexing agent is one or more of EDTA, succinic acid, oxalic acid, oxalate, citric acid and citrate; the metal salt is copper salt and/or iron salt.

The pretreated material is sequentially immersed in a complexing agent for 1-6 hours and in a metal salt solution for 1-6 hours, both at normal temperature.

In the electro-Fenton system, the electro-Fenton cathode material is used as the cathode, the dissolved oxygen in the water is reduced on the surface of the activated carbon fiber to generate hydrogen peroxide, and the obtained hydrogen peroxide reacts with the metal ion complex supported on the surface of the activated carbon fiber to generate hydroxyl groups Free radicals, oxidative degradation of organic pollutants.

The dissolved oxygen in the water is reduced on the surface of the activated carbon fiber cathode to generate hydrogen peroxide. Environmental conditions: pH is 2-10, and temperature is 20-90°C.

In the electro-Fenton system, platinum, graphite, boron-doped diamond or metal oxides (RuO ₂ /Ti, IrO ₂ /Ti, PbO ₂ /Ti or SnO ₂ /Ti) are used as anodes.

The electro-Fenton cathode material and the counter electrode can also form an electrolytic cell, the water flow state is static or flowing, and the electrolysis reaction is carried out at a current density of 0-20 mA/cm ² excluding 0 mA/cm ² .

In the application system of the present invention, the cathode area is injected with air or oxygen, or the oxygen generated by the electrolysis of water at the anode is used to generate hydrogen peroxide in situ.

Compared with the prior art, the beneficial effects of the present invention are:

1. Compared with the conventional heterogeneous Fenton reagent, this method does not need to add hydrogen peroxide externally, which effectively avoids the danger in transportation and storage, and can control the output and output of hydrogen peroxide by controlling the current and voltage. rate of degradation of organic matter.

2. The method uses activated carbon fiber as the cathode, which has the characteristics of adsorption, conductivity, high specific surface area, etc., and has the properties of quasi-three-dimensional electrode, which increases the electrode surface per unit cell volume, and improves the current efficiency and treatment effect.

3. This method loads iron ions or copper ion complexes on the surface of the carbon material cathode, which can effectively catalyze the decomposition of hydrogen peroxide to generate hydroxyl radicals in the range of pH 2 to 10, which improves the traditional Fenton technology. The disadvantage of large amount of iron sludge has good economic, environmental and social benefits.

Description of drawings

Fig. 1 is the application principle diagram of the present invention.

Figure 2 is a scanning electron microscope picture of the activated carbon fiber loaded with ferric citrate according to the present invention.

Figure 3 shows the removal of ibuprofen by activated carbon fiber adsorption, activated carbon fiber electrification, activated carbon fiber loaded with ferric citrate (heterogeneous), activated carbon fiber + ferric citrate (homogeneous), and activated carbon fiber + ferrous sulfate (homogeneous) Schematic diagram of the effect comparison.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

The preparation of an electro-Fenton cathode material based on a loaded activated carbon fiber of the present invention comprises the following steps:

(1) Pretreatment: use viscose-based activated carbon fiber, phenolic-based activated carbon fiber, pitch-based activated carbon fiber or polyacrylonitrile-based activated carbon fiber as the cathode base material of activated carbon fiber, first soak it with acetone or absolute ethanol ultrasonically for 10 to 30 minutes, After cleaning, ultrasonically soak with 1-3 mol/L nitric acid solution for 10-30 minutes, and finally wash with deionized water, and then dry for use.

(2) get the pretreated material and immerse it in a complexing agent and a metal salt solution in turn; the complexing agent can be one of ethylenediaminetetraacetic acid, succinic acid, oxalic acid, oxalate, citric acid and citrate one or several species; the metal salts are copper salts and/or iron salts. The activated carbon fibers were immersed in the complexing agent for 1 to 6 hours, and then in the metal salt solution for 1 to 6 hours, both of which were carried out at room temperature.

(3) Rinse with deionized water and dry for later use.

Fig. 1 is the application principle diagram of the present invention. The dissolved oxygen in the water is electrochemically rapidly reduced on the surface of the cathode to generate hydrogen peroxide in situ, and the hydrogen peroxide reacts with the iron ion complex supported on the surface of the carbon cathode to generate hydroxyl radicals, which oxidatively degrade ibuprofen.

Figure 2 is a scanning electron microscope picture of the activated carbon fiber loaded with ferric citrate complex, and iron citrate complex particles are distributed on the surface of the smooth activated carbon fiber.

As shown in Fig. 3, the electro-Fenton cathode material obtained by the present invention is used in the electro-Fenton system, with platinum, graphite, boron-doped diamond or metal oxide (RuO ₂ /Ti, IrO ₂ /Ti, PbO ₂ /Ti or SnO ₂ /Ti) is the anode, the dissolved oxygen in the water is reduced on the surface of the activated carbon fiber to generate hydrogen peroxide, and the obtained hydrogen peroxide reacts with the metal ion complex supported on the surface of the activated carbon fiber to generate hydroxyl radicals, which oxidatively degrade organic pollutants.

Figure 3 presents the effects of activated carbon fiber adsorption, activated carbon fiber electrification, activated carbon fiber loaded with ferric citrate (heterogeneous), activated carbon fiber + ferric citrate (homogeneous), and activated carbon fiber + ferrous sulfate (homogeneous) versus Blot Schematic diagram of the comparison of the effect of fen removal. It can be seen that the removal of ibuprofen by activated carbon fiber adsorption and electrification (reduction of oxygen to hydrogen peroxide) is not high, while the heterogeneous electro-Fenton shows good ibuprofen removal under near-neutral pH conditions. The removal rate of homogeneous electro-Fenton to ibuprofen was equivalent to 120min under the condition of pH=3. The activated carbon fiber here is loaded with ferric citrate (heterogeneous), which means that the ferric citrate complex is loaded on the surface of the activated carbon fiber; activated carbon fiber + ferric citrate (homogeneous), which means that the ferric citrate is dissolved in the required treatment In solution; activated carbon fiber + ferrous sulfate (homogeneous), which means that ferrous sulfate is dissolved in the solution to be treated.

Embodiment 1 provides the generation rule of hydrogen peroxide and hydroxyl radicals in the electro-Fenton reaction process:

Reaction solution volume: high-purity water 250mL

Reaction solution temperature: 30±2℃

Initial pH of the reaction solution: 6.8

Electrode area: 15cm ² (2.5cm×6cm)

Electrolyte concentration: 0.05M Na ₂ SO ₄

Oxygen flow rate: 100mL/min

Current intensity: 0.05A

Reaction time: 30min, 60min, 90min, 120min

Table 1 Concentration of formed oxides

Generated oxide concentration 30min 60min 90min 120min Hydrogen peroxide concentration (μM) 104.7 141.8 163.2 182.7 Hydroxyl Radical Concentration (μM) 8.6 13.7 20.6 26.1

It can be seen from Example 1 that with the increase of reaction time, the concentrations of generated hydrogen peroxide and hydroxyl radicals increase, indicating that this method can effectively stimulate hydrogen peroxide to generate strong oxidant hydroxyl radicals under neutral pH conditions .

Embodiment 2 illustrates the removal effect of the present invention to different initial concentrations of ibuprofen

Reaction solution volume: high-purity water 250mL

Reaction solution temperature: 30±2℃

Initial pH of the reaction solution: 6.8

Electrode area: 15cm ² (2.5cm×6cm)

Electrolyte concentration: 0.05M Na ₂ SO ₄

Oxygen flow rate: 100mL/min

Current intensity: 0.05A

Response time: 120min

Initial concentration: 1mg/L, 5mg/L, 10mg/L, 20mg/L

Table 2 Removal of different initial concentrations of ibuprofen

Initial concentration (mg/L) 1 5 10 20 Removal rate (%) 98.0 97.5 96.8 94.7

As can be seen from Example 2, the ibuprofen with low and high concentrations of 1 mg/L to 20 mg/L has a relatively good removal, and the ibuprofen with an initial concentration of less than 10 mg/L has more than 95% removal.

Example 3 shows the influence of different current densities on the removal effect of ibuprofen

Reaction solution volume: high-purity water 250mL

Reaction solution temperature: 30±2℃

Initial pH of the reaction solution: 6.8

Initial ibuprofen concentration: 10mg/L

Electrode area: 15cm ² (2.5cm×6cm)

Electrolyte concentration: 0.05M Na ₂ SO ₄

Oxygen flow rate: 100mL/min

Current intensity: 0.05A

Response time: 120min

Initial concentration: 1mA/cm ² , 3mA/cm ² , 5mA/cm ² , 7mA/cm ²

Table 3 Removal of ibuprofen under different current densities

Current density (mA/cm²) 1 3 5 7 Removal rate (%) 89.8 94.3 96.8 97.1

It can be seen from Example 3 that with the increase of the current density, the removal of ibuprofen has increased, and the removal rate of ibuprofen with a current density higher than 5 mA/cm ² is not much different.

Example 4 shows the influence of different operation cycles on the removal effect of ibuprofen

Reaction solution volume: high-purity water 250mL

Reaction solution temperature: 30±2℃

Initial pH of the reaction solution: 6.8

Initial ibuprofen concentration: 10mg/L

Electrode area: 15cm ² (2.5cm×6cm)

Electrolyte concentration: 0.05M Na ₂ SO ₄

Oxygen flow rate: 100mL/min

Current intensity: 0.05A

One cycle: 120min

Table 4 Removal of ibuprofen for different operating cycles

Operation cycle 1 2 3 4 5 6 Removal rate (%) 96.7 90.6 90.7 88.8 87.4 85.3

It can be seen from Example 4 that after 6 operating cycles (12 hours), the removal of ibuprofen is still good (greater than 85%), and the subsequent reloading of ferric citrate can improve the resistance of the electrode to organic pollutants The removal efficiency is high, the loading process conditions are mild, the time is short, and it has a good application prospect.

To sum up, the present invention utilizes the electro-Fenton cathode material based on the supported activated carbon fiber, and the dissolved oxygen generates hydrogen peroxide through a two-electron oxygen reduction reaction on the surface of the activated carbon fiber cathode, and the generated hydrogen peroxide and the iron supported on the surface of the activated carbon fiber. The ion or copper ion complex catalyst reacts to generate strong oxidant hydroxyl radicals, which can oxidize and remove refractory organics under neutral pH conditions. The activated carbon fiber electro-Fenton cathode has a simple preparation method, mild conditions, and in-situ generation of hydrogen peroxide to avoid possible dangers during transportation and storage. Sludge output, no secondary pollution. The raw materials of the invention are cheap and easy to obtain, the preparation method is simple, the treatment period is short, and it is easy to combine with other treatment methods, and is favorable for large-scale production and comprehensive treatment of organic pollutants. Its application is an electro-Fenton wastewater treatment method that can continuously add iron salts, has a wide pH range, and is especially suitable for near-neutral conditions, and has great application prospects.

Claims (7)

1. a preparation based on the electro-Fenton cathode material of loaded activated carbon fiber, is characterized in that, comprises the steps: (1) get the active carbon fiber cathode base material and carry out pretreatment, described pretreatment is to use acetone or absolute ethanol ultrasonic soak first, then use nitric acid solution ultrasonic soak after cleaning, finally wash, dry standby; (2) Immerse the pretreated material in a complexing agent for 1-6 hours in turn, and in a metal salt solution for 1-6 hours, all at room temperature, and the complexing agent is ethylenediaminetetraacetic acid, succinic acid , one or more of oxalic acid, oxalate, citric acid and citrate; the metal salt is copper salt and/or iron salt; (3) Rinse and dry for use. 2. the preparation of the electro-Fenton cathode material based on loaded activated carbon fiber according to claim 1, is characterized in that, described activated carbon fiber cathode base material is viscose-based activated carbon fiber, phenolic-based activated carbon fiber, pitch-based activated carbon fiber or Polyacrylonitrile-based activated carbon fiber. 3. the application of the electro-Fenton cathode material based on loaded activated carbon fiber according to claim 1, is characterized in that, in electro-Fenton system, with this electro-Fenton cathode material as cathode, the dissolved oxygen in water is on the surface of activated carbon fiber The reduction generates hydrogen peroxide, the obtained hydrogen peroxide reacts with the metal ion complex supported on the surface of the activated carbon fiber to generate hydroxyl radicals, and the organic pollutants are oxidatively degraded, and the organic pollutants are ibuprofen. 4 . The application according to claim 3 , wherein, the dissolved oxygen in the water is reduced on the surface of the activated carbon fiber cathode to generate hydrogen peroxide. Environmental conditions: pH is 2-10, and temperature is 20-90° C. 5 . The application according to claim 3, characterized in that, in the electro-Fenton system, platinum, graphite, boron-doped diamond or metal oxide is used as the anode. 6. application according to claim 3, is characterized in that, this electro-Fenton cathode material and counter electrode form electrolytic cell, and water flow state is static or flow dynamic, at 0～20mA/cm ² and does not include 0mA/cm The electrolysis reaction was carried out at a current density of ² . 7. The application according to claim 6, characterized in that, the cathode area is injected with air or oxygen, or hydrogen peroxide is generated in situ by utilizing the oxygen generated by the electrolysis of water at the anode.

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