CN106964331A - A kind of photochemical catalyst/porous carbon fiber composite and its preparation method and application - Google Patents

Abstract

A preparation method of a photocatalyst/porous carbon fiber composite material, first dissolving a solid polymer in an organic solvent to form a spinning solution; then electrospinning the spinning solution to obtain an electrospun precursor; After the silk is pre-oxidized and carbonized, the carbon fiber is obtained; the carbon fiber is activated by KOH, and then washed with 5% HCl solution and distilled water, and dried to obtain the porous carbon fiber; the photocatalyst is loaded on the porous carbon fiber by the hydrothermal method. Wash with water, ethanol and distilled water, and dry to obtain a photocatalyst/porous carbon fiber composite material. The photocatalyst/porous carbon fiber composite material prepared by this method has both the functions of adsorption and catalysis. Because the high specific surface area of carbon fiber can better disperse the photocatalyst and increase the contact area of photocatalysis; the good electrical conductivity of carbon fiber can also Better generate photogenerated electrons and improve photocatalytic efficiency. The whole preparation process has mild conditions, simple operation and is suitable for mass production.

Description

A kind of photocatalyst/porous carbon fiber composite material and its preparation method and application

technical field

The invention relates to the technical field of preparation of composite materials.

technical background

In recent years, with the development of my country's industry, environmental pollution has seriously affected people's life and health, and has become an urgent problem to be solved in our country. Photocatalytic treatment technology has been widely concerned because it can reduce organic pollutants to inorganic substances, and has fast reaction rate, high light utilization efficiency and no secondary pollution. Among them, how to improve the ability of photocatalytic materials to deal with environmental pollution (especially water pollution) has become a research hotspot. One of the methods is to combine carbon with photocatalyst, and use the electrical conductivity of carbon to improve the performance of photocatalyst. For example, Chinese invention patent application 201510827373.0 introduced a method for preparing a photocatalytic material that uses a sol-gel method to combine metal oxides and carbon nanotubes, but the sol-gel method is complicated to operate, and metal oxides are easy to accumulate, and Carbon nanotubes cannot provide more adsorption pores. However, this invention proves that combining carbon materials and photocatalysts can better treat organic wastewater. This invention proposes a new photocatalyst/carbon material composite material. In this paper, a simpler hydrothermal method is used to load the photocatalyst. The carbon carrier adopts electrospinning. The electrospinning method can prepare nano-scale carbon fibers, and the adsorption capacity of carbon fibers is enhanced by KOH activation to make pores, so that this material can be used to the greatest extent. play a role in the treatment of pollutants.

Contents of the invention

The purpose of this invention is to provide a kind of photocatalyst/porous carbon fiber composite material and preparation method thereof, compared with the hydrothermal method traditionally applied to granular, rod-shaped, spherical, because the large specific surface area of carbon fiber is applied to the hydrothermal method on carbon fiber The photocatalyst can be better dispersed, so that the carbon fiber has both adsorption and catalytic functions, and the whole preparation process has mild conditions, simple operation, and is suitable for mass production.

First aspect of the invention:

A photocatalyst/porous carbon fiber composite material, including porous carbon fiber as a carrier, and a photocatalyst loaded on its surface.

The photocatalyst is CeO ₂ or ZnO.

The second aspect of the present invention: a method for preparing a photocatalyst/porous carbon fiber composite material,

Include the following steps:

(1) Dissolving the solid polymer in an organic solvent to form a spinning precursor;

(2) Electrospinning the spinning precursor to obtain an electrospun precursor;

(3) Pre-oxidize and carbonize the electrospun precursors to obtain carbon fibers;

(4) carbon fiber is activated by KOH, then washed with 5% HCl solution and distilled water, and dried to obtain porous carbon fiber;

(5) Load the photocatalyst on the porous carbon fiber by hydrothermal method, wash with absolute ethanol and distilled water, and dry to obtain the photocatalyst/porous carbon fiber composite material.

The invention utilizes the electrospinning method to produce in large quantities, and is simple and easy to prepare carbon fibers, and utilizes an activation method to change the carbon fibers into porous carbon fibers, thereby improving its adsorption performance, and then prepares a photocatalyst/porous carbon fiber composite material through hydrothermal loading .

Further, the high polymer of the present invention is polyacrylonitrile (PAN) or povidone (PVP). PAN or PVP is a high polymer that is easy to spin, which improves the operability of the spinning process.

The organic solvent is absolute ethanol or dichloromethane (DMF). These solvents can better dissolve PAN or PVP, which is convenient for spinning.

The spinning voltage of the electrospinning is 15kV, the receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the flow rate of the spinning solution is 2mm/min, and the inclination angle of the syringe is 15°. Under this condition, the spinning process is easier to operate and easy to form into filaments.

The ambient temperature of the pre-oxidation is 250° C., and the pre-oxidation time is 2 hours. The pre-oxidation of the fiber precursors at this temperature and time can make the polymers in the precursors undergo cyclodehydrogenation into a high-temperature-resistant trapezoidal structure, so as to ensure the stability of the precursors under high-temperature carbonization.

The carbonization is carried out in nitrogen (N ₂ ), the heating rate is 5° C./min, and the temperature is maintained at 800° C. for 2 hours, which can make the carbonization more complete and the carbon content higher.

The activation condition is that the mass ratio of carbon fiber to KOH is 3:4, the carbon fiber is immersed in the KOH solution for 2 hours, and then dried in an oven at 80°C, and then the dried carbon fiber is placed in a tube furnace, from room temperature to Raise the temperature to 800°C at 10°C/min, keep it warm for 30min and then cool down to room temperature. Activated under this condition, the specific surface area and pore distribution of the fiber are better.

The photocatalysts are CeO ₂ , ZnO, etc., which are cheap and easy to obtain.

A third aspect of the present invention:

The application of the photocatalyst/porous carbon fiber composite material in the degradation of wastewater containing organic matter.

Advantage of the present invention and positive effect are:

1. The present invention can be mass-produced by electrospinning, and is simple and easy to prepare carbon fibers, and uses activation means to change carbon fibers into porous carbon fibers to improve its adsorption performance, and then prepare photocatalyst/porous carbon fibers by hydrothermal loading composite material.

2. The photocatalyst/porous carbon fiber composite material prepared by this method has both the functions of adsorption and catalysis, especially by activating the carbon fiber to form pores, which improves the adsorption function of carbon fiber to a certain extent and enhances its removal of pollutants Effect.

3. Due to the high specific surface area of carbon fiber, it can better disperse the photocatalyst and increase the contact area of photocatalysis; the good conductivity of carbon fiber can also better guide the photogenerated electrons and improve the photocatalytic efficiency.

4. Both the electrospinning method and the hydrothermal method adopted in the method are simple and feasible and can be mass-produced. Economically, the preparation cost can be reduced and the economic benefit of the process can be improved.

5. The traditional hydrothermal method applied to granular, rod and spherical shapes is easy to cause accumulation. Due to the large specific surface area of carbon fiber, the hydrothermal method applied to carbon fiber can better disperse the photocatalyst, thereby improving its photocatalytic effect.

Description of drawings

Figure 1 is a flow chart of the preparation of photocatalyst/porous carbon fiber composites.

Figure ₂ is the SEM image of the photocatalyst/porous carbon fiber composite material prepared with PAN as the polymer and CeO2 as the photocatalyst.

Fig. ₃ is the SEM image of the photocatalyst/porous carbon fiber composite material prepared by using PVP as the high polymer and the photocatalyst as CeO2.

Figure 4 is a comparison diagram of CeO ₂ particles prepared by traditional hydrothermal method and photocatalyst/porous carbon fiber composite prepared by CeO ₂ .

Fig. 5 is a graph showing the removal rate of CeO ₂ particles and CeO ₂ /porous carbon fiber composites prepared by traditional hydrothermal method for methylene blue.

detailed description

The percentages (%) described in the description of the present invention all refer to mass percentages unless otherwise specified.

1. The process of preparing photocatalyst/porous carbon fiber composite material:

Embodiment 1: take PAN as high polymer, photocatalyst is CeO ₂

1. Weigh 1.5g of PAN, dissolve in 15g of DMF, and dissolve completely under magnetic stirring to obtain the spinning solution precursor. Install the spinning solution precursor on the electrospinning equipment for spinning, the spinning voltage is 15kV, the receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the spinning solution flow rate is 2mm/min, the syringe The inclination angle is 15°, and the PAN precursor is obtained after electrospinning.

2. Pre-oxidize the PAN precursor in air at 250°C at a heating rate of 5°C/min for 2 hours, and then carbonize at 800°C for 2 hours at a heating rate of 5°C/min in _N2 to obtain carbon fibers.

3. The mass ratio of carbon fiber to KOH is 3:4, immerse the carbon fiber in the KOH solution for 2 hours, and then dry it in an oven at 80°C, then place the dried carbon fiber in a tube furnace, from room temperature to 10°C /min to raise the temperature to 800°C, keep it warm for a certain period of time, and then lower it to room temperature, then wash it with 5% HCl solution and distilled water, and dry it to obtain porous carbon fibers.

4. Mix 0.1g of porous carbon fiber into the mixed solution of 0.3g Ce(NO ₃ ) ₃ 6H ₂ O and 2.5g CO(NH ₂ ) ₂ , mix and stir for 10min, transfer the mixed solution to 100mL stainless steel hydrothermal synthesis high pressure reaction kettle, and reacted at a constant temperature of 160°C for 24h in an electric thermostat blast drying oven. After the reaction, the carbon fibers in the reactor were repeatedly washed with ethanol and double distilled water, and dried at 60° C. for 12 hours to obtain the CeO ₂ /porous carbon fiber composite material. The SEM image of the obtained material is shown in Figure 2.

Embodiment 2: take PVP as high polymer, photocatalyst is CeO ₂

1. Weigh 1.5g of PVP, dissolve it in 15g of DMF, and dissolve it completely under magnetic stirring to obtain the doping solution precursor. Install the spinning solution precursor on the electrospinning equipment for spinning, the spinning voltage is 15kV, the receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the spinning solution flow rate is 2mm/min, the syringe The inclination angle is 15°, and the PVP precursor is obtained after electrospinning.

2. Pre-oxidize the PVP precursor in air at 250°C at a heating rate of 5°C/min for 2 hours, and then carbonize it in _N2 at a heating rate of 5°C/min at 800°C for 2 hours to obtain carbon fibers.

3. The mass ratio of carbon fiber to KOH is 3:4, immerse the carbon fiber in the KOH solution for 2 hours, and then dry it in an oven at 80°C, then place the dried carbon fiber in a tube furnace, from room temperature to 10°C /min to raise the temperature to 800°C, keep it warm for a certain period of time, and then lower it to room temperature, then wash it with 5% HCl solution and distilled water, and dry it to obtain porous carbon fibers.

4. Mix 0.1g of porous carbon fiber into the mixed solution of 0.3g Ce(NO ₃ ) ₃ 6H ₂ O and 2.5g CO(NH ₂ ) ₂ , mix and stir for 10min, transfer the mixed solution to 100mL stainless steel hydrothermal synthesis high pressure reaction kettle, and reacted at a constant temperature of 160°C for 24h in an electric thermostat blast drying oven. After the reaction, the carbon fibers in the reactor were washed repeatedly with ethanol and double distilled water, and dried at 60°C for 12 hours to obtain the CeO ₂ /porous carbon fiber composite material. The SEM image of the obtained material is shown in Figure 3.

Embodiment 3: take PAN as high polymer, photocatalyst is ZnO

1. Weigh 1.5g of PAN, dissolve in 15g of DMF, and dissolve completely under magnetic stirring to obtain the spinning solution precursor. Install the spinning solution precursor on the electrospinning equipment for spinning, the spinning voltage is 15kV, the receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the spinning solution flow rate is 2mm/min, the syringe The inclination angle is 15°, and the PAN precursor is obtained after electrospinning.

2. Pre-oxidize the PAN precursor in air at 250°C for 2 hours at a heating rate of 5°C/min, and then carbonize in N2 at a heating rate of 5°C/min at 800°C for 2 hours to obtain carbon fibers.

3. The mass ratio of carbon fiber to KOH is 3:4, immerse the carbon fiber in the KOH solution for 2 hours, and then dry it in an oven at 80°C, then place the dried carbon fiber in a tube furnace, from room temperature to 10°C /min to raise the temperature to 800°C, keep it warm for a certain period of time, and then lower it to room temperature, then wash it with 5% HCl solution and distilled water, and dry it to obtain porous carbon fibers.

4. Mix 0.1g of porous carbon fiber in 0.4g of zinc acetate solution, adjust the pH to 10 with NaOH solution with a concentration of 0.5mol/L, continue to stir for 10min, and transfer the mixture to 100mL stainless steel hydrothermal synthesis for high-pressure reaction Kettle, and react at a constant temperature of 160°C for 24h in an electric thermostat blast drying oven. After the reaction, the carbon fibers in the reactor were repeatedly washed with ethanol and double distilled water, and dried at 60° C. for 12 hours to obtain the ZnO/porous carbon fiber composite material.

Embodiment 4: take PVP as high polymer, photocatalyst is ZnO

1. Weigh 1.5g of PVP, dissolve it in 15g of DMF, and dissolve it completely under magnetic stirring to obtain the doping solution precursor. Install the spinning solution precursor on the electrospinning equipment for spinning, the spinning voltage is 15kV, the receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the spinning solution flow rate is 2mm/min, the syringe The inclination angle is 15°, and the PVP precursor is obtained after electrospinning.

2. Pre-oxidize the PVP precursor in air at 250°C at a heating rate of 5°C/min for 2 hours, and then carbonize it in _N2 at a heating rate of 5°C/min at 800°C for 2 hours to obtain carbon fibers.

3. The mass ratio of carbon fiber to KOH is 3:4, immerse the carbon fiber in the KOH solution for 2 hours, and then dry it in an oven at 80°C, then place the dried carbon fiber in a tube furnace, from room temperature to 10°C /min to raise the temperature to 800°C, keep it warm for a certain period of time, and then lower it to room temperature, then wash it with 5% HCl solution and distilled water, and dry it to obtain porous carbon fibers.

4. Mix 0.1g of porous carbon fiber in 0.4g of zinc acetate solution, adjust the pH to 10 with NaOH solution with a concentration of 0.5mol/L, continue to stir for 10min, and transfer the mixture to 100mL stainless steel hydrothermal synthesis for high-pressure reaction Kettle, and react at a constant temperature of 160°C for 24h in an electric thermostat blast drying oven. After the reaction, the carbon fibers in the reactor were repeatedly washed with ethanol and double distilled water, and dried at 60° C. for 12 hours to obtain the ZnO/porous carbon fiber composite material.

Embodiment 5: traditional hydrothermal method prepares CeO ₂ preparation process

1. Weigh 0.3g Ce(NO ₃ ) ₃ ·6H ₂ O and 2.5g CO(NH ₂ ) ₂ to dissolve in deionized water, mix and stir for 10 minutes. The mixed solution was transferred to a 100mL stainless steel hydrothermal synthesis autoclave, and reacted at a constant temperature of 160°C for 24h in an electric constant temperature blast drying oven. After the reaction, the white reaction precipitate in the reaction kettle was repeatedly washed with ethanol and double distilled water, and then the obtained product was dried at 60° C. for 12 hours, and ground with an agate mortar. Finally, the white solid powder was calcined in a tube furnace at a constant temperature of 300° C. for 3 hours to obtain a light yellow powdery solid, namely CeO ₂ .

2. Compare the CeO ₂ /porous carbon fiber composite material prepared in Example 1 with the CeO ₂ prepared by the traditional hydrothermal method, and compare the particle size and distribution of the two CeO ₂ through SEM images. The results are shown in Figure 4 and Table 1 below.

Table 1 The particle size and distribution of CeO ₂

It can be seen from Figure 4 that the accumulation of CeO ₂ prepared by the traditional hydrothermal method is serious, and the particle size is relatively large. When CeO ₂ is loaded on the porous carbon fiber, the large specific surface area of the porous carbon fiber can better disperse CeO ₂ and The particle size is reduced, which is more conducive to improving the catalytic effect.

Example _{6 :} Treatment of CeO2 particles, porous carbon fibers, CeO2/porous carbon fiber composites for methylene blue

Prepare 5mg/L of methylene blue as a photocatalytic degradation solution. Take 100mL of methylene blue solution each time and put it in a 250mL beaker. Install a 40W UV lamp on the top of the beaker. The distance between the UV lamp and the beaker is 15cm. Add 0.1g of CeO ₂ particles (porous carbon fiber, mixture of CeO ₂ particles and porous carbon fiber, CeO ₂ /porous carbon fiber composite material) under certain conditions, and start timing from turning on the UV lamp power supply, every 20min, take the suspension, centrifuge Take the supernatant, measure the absorbance with a spectrophotometer, and calculate the degradation rate.

The results are shown in Figure 5 and Table 2 below.

Table 2 methylene blue removal rate (120min)

It can be seen from Figure ₅ that under the condition of no light, the CeO ₂ particles prepared by the traditional hydrothermal method have no removal effect, while the removal effect of the porous carbon fiber is about 30%. The rate reaches 70%, which is obviously better _than CeO2 particles prepared by traditional hydrothermal method. From the curve of 20min to 120min, the slope of the CeO2/porous carbon fiber composite curve is significantly higher _than the slope of the CeO2 particle curve, which shows that the CeO2 _on the _CeO2 /porous carbon fiber composite has a better effect _on methylene blue wastewater. Catalytic rate, which is mainly due to the size reduction of CeO2 and the synergistic effect of carbon fiber and _{CeO2 ;} in addition, the treatment effect of simultaneously adding _CeO2 particles and porous carbon fiber in the solution is still not as good as that of _CeO2 /porous carbon fiber composite, The main reason is that when CeO ₂ particles are added to the surface of the porous carbon fiber by loading, the photocatalytic effect of CeO ₂ can be enhanced by the adsorption of the porous carbon fiber.

Claims (10)

1. A photocatalyst/porous carbon fiber composite material, characterized in that it includes a porous carbon fiber as a carrier, and a photocatalyst loaded on its surface. 2. The photocatalyst/porous carbon fiber composite material according to claim 1, characterized in that, the photocatalyst is CeO ₂ or ZnO. 3. The preparation method of photocatalyst/porous carbon fiber composite material is characterized in that, comprises the following steps: (1) Dissolving the solid polymer in an organic solvent to form a spinning precursor; (2) Electrospinning the spinning precursor to obtain an electrospun precursor; (3) Pre-oxidize and carbonize the electrospun precursors to obtain carbon fibers; (4) carbon fiber is activated by KOH, then washed with 5% HCl solution and distilled water, and dried to obtain porous carbon fiber; (5) Load the photocatalyst on the porous carbon fiber by hydrothermal method, wash with absolute ethanol and distilled water, and dry to obtain the photocatalyst/porous carbon fiber composite material. 4. The preparation method according to claim 1, characterized in that: the solid polymer is PAN or PVP; the organic solvent is dehydrated alcohol or DMF; the spinning voltage of the electrospinning is 15kV, The receiving distance is 20cm, the ambient temperature is ≤40°C, the ambient humidity is ≤30%, the flow rate of the spinning solution is 2mm/min, and the inclination angle of the injector is 15°. 5. The preparation method according to claim 1, characterized in that: the pre-oxidation condition is oxidation in air at 250° C. for ₂ h at a heating rate of 5° C./min; the carbonization condition is N in Carbonization at 800°C for 2h at a heating rate of 5°C/min. 6. The preparation method according to claim 1, characterized in that: the activation condition is that the mass ratio of carbon fiber to KOH is 3:4, the carbon fiber is immersed in the KOH solution for 2 hours, then dried in an oven at 80°C, and then Place the dried carbon fibers in a tube furnace, raise the temperature from room temperature to 800 °C at a rate of 10 °C/min, keep the temperature for 30 min, and then cool down to room temperature. 7. The preparation method according to claim 1, characterized in that: the photocatalyst is CeO ₂ or ZnO. 8. The preparation method according to claim 1, characterized in that: the photocatalyst is CeO ₂ , and the condition of the hydrothermal method is to mix 0.1 g of porous carbon fiber with 0.3 g of Ce(NO ₃ ) ₃ ·6H ₂ O and 2.5 g CO(NH ₂ ) ₂ mixed solution, mixed and stirred for 10min, transferred the mixed solution to a 100mL stainless steel hydrothermal synthesis autoclave, and reacted at a constant temperature of 160°C for 24h in an electric constant temperature blast drying oven; after the reaction , the carbon fibers in the reactor were repeatedly washed with ethanol and double distilled water, and dried at 60°C for 12 hours to obtain CeO ₂ /porous carbon fiber composite materials. 9. The preparation method according to claim 1, characterized in that: the photocatalyst is ZnO, and the hydrothermal method condition is that 0.1g porous carbon fiber is mixed in 0.4g zinc acetate solution, and the concentration of the substance used is 0.5mol /L NaOH solution to adjust the pH to 10, continue to stir for 10 minutes, transfer the mixed solution to a 100mL stainless steel hydrothermal synthesis autoclave, and react at a constant temperature of 160°C for 24 hours in an electric constant temperature blast drying oven; after the reaction, put The carbon fibers in the reactor were washed repeatedly with ethanol and double distilled water, and dried at 60° C. for 12 hours to obtain the ZnO/porous carbon fiber composite material. 10. The application of the photocatalyst/porous carbon fiber composite material as claimed in claim 1 in the degradation of wastewater containing organic matter.