TWI566830B - Preparation of Photocatalyst Composite Nanofibers - Google Patents

Description

Photocatalytic composite nanofiber production method

The invention relates to a photocatalyst composite nanofiber, in particular to a visible light photocatalyst composite nanofiber and a preparation method thereof.

Since organic pollutants (such as dyes) in wastewater are difficult to be biodegraded and are extremely resistant to light, heat and oxidation, it is generally catalyzed by titanium dioxide photocatalyst to prevent degradation and other secondary pollution. However, the titanium dioxide photocatalyst needs to be excited by the ultraviolet light source to produce a catalytic effect, and the ultraviolet light energy in sunlight is only about 3 to 5% of the total energy (about 43% of visible light and about 45% of infrared light), so that the titanium dioxide photocatalyst The scope of application is greatly limited.

Generally, a transition metal (for example, platinum, palladium, rhodium, gold, or silver) is doped into the titanium dioxide photocatalyst to shift the absorption band from the ultraviolet region to the visible region. However, its thermal stability and rate of degradation of organic pollutants through visible light still need to be improved.

Accordingly, it is an object of the present invention to provide a photocatalytic composite nanofiber which can effectively utilize visible light to degrade pollutants.

Thus, the photocatalyst composite nanofiber of the present invention comprises dioxane a fibrous body formed of titanium oxide and graphene oxide; and a particulate transition metal distributed on the surface of the fiber body.

Therefore, another object of the present invention is to provide a photocatalytic composite nanofiber preparation method comprising the steps of: mixing a titanium-containing precursor, an organic polymer, a stabilizer, and an organic solvent to obtain an initial solution; Mixing an aqueous solution of graphene oxide with the initial solution to obtain a bulk solution; mixing a transition metal ion and a chelating agent with the main solution and heating to obtain an electrospinning solution; and forming the electrospinning solution by electrospinning Multiple nanofibers.

The effect of the invention is that the photocatalyst composite nanofiber obtained by the sol-gel method combined with the electrospinning technology has the advantages of small diameter, large specific surface area, high thermal stability and high visible light degradation efficiency. Features help to treat pollutants in wastewater.

Hereinafter, the present invention will be described in detail. Preferably, the photocatalyst composite nanofiber of the present invention has a diameter of 50 to 150 nm. More preferably, the photocatalyst composite nanofiber of the present invention has a diameter of 85 to 110 nm.

Preferably, the transition metal is selected from the group consisting of silver, palladium, rhodium, gold, ruthenium, cobalt, nickel, zirconium or combinations thereof. More preferably, the transition metal is silver.

Preferably, the weight ratio of the transition metal ion to the titanium-containing precursor ranges from 1:6000 to 500:6000, and the weight ratio of the graphene oxide to the titanium-containing precursor ranges from 0.0001:6000 to 500:6000. More preferably, the weight ratio of the graphene oxide to the titanium-containing precursor ranges from 0.002:6000 to 10:6000.

Preferably, the transition metal ion is a silver ion.

Preferably, the organic polymer is selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinyl acetate (PVA), polyethylene glycol (PEG) or pluronic®. In a specific embodiment of the invention, the organic polymer is polyvinylpyrrolidone.

Preferably, the stabilizer is acetic acid. Preferably, the volume ratio of the stabilizer to titanium tetraisopropoxide ranges from 8:6 to 10:6.

Preferably, the chelating agent is an indigo dye.

Preferably, after forming the nanofibers, a calcination step of heating the nanofibers is further included. More preferably, the calcination temperature is 450 to 600 °C. In a particular embodiment of the invention, the calcination temperature is 450 °C.

Preferably, the electrospinning electrospinning port to the collector has a distance of 1 to 50 cm. In a specific embodiment of the invention, the distance from the electrospin to the collector is 12 to 13 cm.

Preferably, the electrospinning solution has an injection flow rate of 0.001 to 1 mL/min. In a specific embodiment of the invention, the electrospinning solution has an injection flow rate of 0.086 mL/min.

Preferably, the voltage of the electrospinning is 0.1 to 300 kV. In a specific embodiment of the invention, the electrospinning voltage is 17 kV.

The invention is further described in the following examples, but it should be understood that these examples are for illustrative purposes only and are not to be construed as limiting.

Example

<Example 1> Photocatalyst composite fiber E1

[Preparation of initial solution (TiO ₂ Solution)]

6 mL of titanium (IV) isopropoxide (TIP) was mixed with 8 mL of acetic acid (as a stabilizer) to form a titanium-containing precursor solution.

2 g of polyvinylpyrrolidone (PVP, weight average molecular weight of 1,300,000) was dissolved in 18 g of ethanol (PVP ratio was 10 wt%) to form a PVP solution.

The titanium-containing precursor solution and the PVP solution were mixed and stirred to obtain an initial solution (TiO ₂ solution).

[Preparation of main body solution (TiO ₂ /GO solution)]

3 g of graphite and 3 g of sodium nitrate were placed in a 1 L glass three-necked reaction flask, and then 138 mL of sulfuric acid (purity ≧90 wt%) was added and vortexed for 5 minutes in an ultrasonic wave, and then stirred in an ice bath at 0 to 4 ° C for 10 minutes while being slow. After adding 9 g of potassium permanganate, the mixture was stirred for 24 hours, 150 mL of deionized water was slowly added, 350 mL of deionized water was added, and finally 30 mL of a 30 wt% aqueous solution of H ₂ O _{2 was} added to terminate the oxidation reaction. After standing for 24 hours, the precipitate was centrifuged, and the precipitate was washed with 1 L of hydrochloric acid (HCl: H ₂ O = 1:10), washed with deionized water to pH 7, and finally dehydrated by lyophilization, and then 10 mg. The dried precipitate was placed in 20 mL of water (corresponding to 0.5 mg/mL) and vortexed at room temperature for several hours to ensure a uniformly dispersed aqueous graphene oxide solution.

0.5 mL of the above aqueous graphene oxide solution was slowly added to the above initial solution and stirred for 10 minutes, and then ultrasonically shaken at 60 ° C for 1 hour to obtain a bulk solution (TiO ₂ /GO solution).

[Preparation of electrospinning solution (TiO ₂ /GO/Ag solution)]

8 mg of silver nitrate was added to the above main solution and stirred for 10 minutes, a phthalocyanine dye (as a chelating agent) was added to a concentration of 1 wt% and stirred for 10 minutes, and then ultrasonically shaken at 60 ° C for 1 hour, and then stirred. After 1 day, an electrospinning solution (TiO ₂ /GO/Ag solution) was obtained.

[electrospinning and calcination]

The electrospinning solution was electrospun [Electrical spinning equipment and working parameters were set as follows: electrospinning (stainless steel needle) to collector (aluminum foil roller, diameter 22 cm, width 10 cm), the distance was 12~13 cm, solution flow rate It is 0.086 mL/min, the voltage is 17 kV, the roller rotation speed is 1200 rpm], to form fibers, and the collected fibers are coated with aluminum foil, placed in a high-temperature calcining furnace, and heated and sintered at 450 ° C for 1 hour to obtain an implementation. Photocatalyst composite fiber E1 of Example 1.

<Example 2> Photocatalyst composite fiber E2

Example 2 is similar to the process of Example 1, except that the amount of acetic acid in the preparation initial solution was changed to 10 mL, and the amount of silver nitrate in the preparation of the electrospinning solution was changed to 32 mg to obtain the photocatalyst composite of Example 2. Fiber E2.

<Examples 3 to 4> Photocatalyst composite fibers E3 to E4

Examples 3 to 4 were similar to the processes of Examples 1 to 2, except that the amount of dry precipitate in the preparation of the main body solution was changed to 400 mg (corresponding to 20 mg/mL), and the photocatalysts of Examples 3 to 4 were respectively obtained. Composite fiber E3~E4.

<Comparative Example 1> Photocatalyst fiber CE1

The initial solution (TiO ₂ solution) of the above Example 1 was further stirred for 1 day, and then electrospinning and calcination as described above were directly carried out to obtain a photocatalyst fiber CE1 of Comparative Example 1.

<Comparative Example 2> Photocatalyst composite fiber CE2

The main solution (TiO ₂ /GO solution) of the above Example 1 was further stirred for 1 day, and then electrospinning and calcination were carried out as described above to obtain a photocatalyst composite fiber CE2 of Comparative Example 2.

<Comparative Example 3 to 5> Photocatalyst Composite Fiber CE3~CE5

Comparative Examples 3 to 5 were similar to the process of Comparative Example 2 except that the amount of dry precipitate in the preparation of the main solution was changed to 40, 200, and 400 mg (equivalent to 2, 10, 20 mg/mL), respectively. Photocatalyst composite fibers CE3 to CE5 of Comparative Examples 3 to 5.

Observation and testing

In the above process for preparing the main body solution, if the amount of the dried precipitate is more than 400 mg (corresponding to 20 mg/mL), a partial precipitation may occur to obtain a uniformly dispersed aqueous graphene oxide solution, and the precipitated portion may not be dispersed by electrospinning. In the fiber. If the amount of the aqueous graphene oxide solution is more than 0.5 mL, the viscosity of the main solution and the electrospinning solution may be too high. It is impossible to smoothly form silk by electrospinning.

In the above process for preparing the electrospinning solution, if the amount of silver nitrate is more than 32 mg (for example, 48 mg or 80 mg), the viscosity of the electrospinning solution may be too high to be smoothly formed by electrospinning, or even jelly-like. Electrospinning.

<Electron Microscope Observation>

The fibers E1 to E4 and CE1 to CE5 of Examples 1 to 4 and Comparative Examples 1 to 5 were cut into appropriate sizes, attached to a metal stage, and the metal stage was placed in a gold plating machine and plated with platinum under vacuum. The structure was observed by a field emission scanning electron microscope (FE-SEM, available from JEOL, model JSM-7000F), and the diameter of the fiber (n=30) was measured using Image J software. The results are shown in Table 1 below. Shown.

It can be seen from Table 1 that the photocatalyst composite fibers E1 to E4 of Examples 1 to 4 have a diameter of about 86 to 109 nm, and the fibers CE1 to CE5 of Comparative Examples 1 to 5 have a diameter of about 205 to 500 nm, which shows the photocatalyst composite of the present invention. The scale of the fiber is on the nanometer scale and the diameter is significantly smaller.

It can be observed from the electron micrograph that the photocatalyst conjugate fibers E1 to E4 of Examples 1 to 4 and the fibers CE2 to CE5 of Comparative Examples 2 to 5 are uniformly dispersed with bead-like ridged micelles, and the ridges in CE2 to CE5 are raised. The microcapsules became more pronounced as the amount of graphene oxide in the process increased, while the fiber CE1 of Comparative Example 1 did not have the raised micelles, so it was presumed that graphene oxide was coated in the fibers to cause bulging.

Further, it can be observed from the electron micrograph that the photocatalyst composite fibers E1 to E4 of Examples 1 to 4 have a plurality of granular nanoparticle distributions on the surface (the diameter of the nanoparticles in E1 and E3 is about 6). ~13nm, the diameter of the nanoparticles in E2 and E4 is about 16~31nm), and the surface of the fibers CE1~CE5 of Comparative Examples 1~5 does not have the distribution of nanoparticles. Therefore, it is presumed that the nanoparticles are Silver nanoparticles.

<Temperature Gravimetric Analysis (TGA)>

The fibers E1 to E4 and CE1 to CE5 of Examples 1 to 4 and Comparative Examples 1 to 5 were measured for 10% thermogravimetric loss by a thermogravimetric analyzer (available from TA Instruments, model TGA-250). Temperature T _d10% (The operating parameters were set as follows: nitrogen flow rate was 20 mL/min, temperature range was 30-600 ° C, heating rate was 10 ° C/min), and the results are shown in Table 2 below.

It can be seen from Table 2 that the 10% thermogravimetric loss temperature of the photocatalyst composite fibers E1 to E4 of Examples 1 to 4 is about 330 to 357 ° C; the 10% thermogravimetric loss temperature of the fibers CE1 to CE5 of Comparative Examples 1 to 5 It is about 298-338 ° C, which shows that the thermal stability of the photocatalyst composite fiber of the present invention is significantly higher.

<Specific surface area test>

The specific surface areas of fibers E1 to E2 and CE1 to CE5 of Examples 1 to 2 and Comparative Examples 1 to 5 were measured by a nitrogen adsorption method using a BET specific surface area measuring instrument (purchased from Micromeritics, model ASAP 2010). The results are as follows. Table 3 shows.

As can be seen from Table 3, the photocatalyst composite fibers E1 to E2 of Examples 1 and 2 have a specific surface area of about 98 to 99 m ² /g; and the fibers CE1 to CE5 of Comparative Examples 1 to 5 have a specific surface area of about 40 to 76 m ^{2 .} /g, showing that the photocatalyst composite fiber of the present invention has a large specific surface area, and it is advantageous for adsorbing more pollutants per unit weight.

<visible light degradation test>

0.01 g of the above-mentioned fibers E1 to E4 and CE1 to CE5 of Examples 1 to 4 and Comparative Examples 1 to 5 were placed in 20 mL of a methylene blue aqueous solution having a concentration of 20 ppm (as a hypothetical pollution source), and fluorescent tubes (purchased from Philips, model TL-D 18 W/865) as a visible light source, placed a piece of anti-UV glass in front of the visible light source (to block light with a wavelength below 400 nm) and then subjected to visible light degradation test. After 48 hours of degradation, remove a small amount. The methylene blue solution was centrifuged, and the absorbance of the maximum absorption peak (about 665 nm) at a wavelength of 500 to 700 nm was measured by an ultraviolet-visible spectrometer, and the total degradation rate of methylene blue was calculated by the following formula (I). The results are shown in Table 4 below.

Replace the above with a 10ppm aqueous solution of methyl orange (pH 3) 20ppm methylene blue aqueous solution was used as a hypothetical pollution source for the above visible light degradation test. After 48 hours of degradation, a small amount of methyl orange aqueous solution was taken out, centrifuged by a centrifuge, and the maximum absorption peak at a wavelength of 400-600 nm was measured by an ultraviolet-visible spectrometer. The absorbance (about 500 nm), and the total degradation rate of methyl orange was calculated as in the above formula (I), and the results are shown in Table 4 below.

It can be seen from Table 4 that the total degradation rate of methylene blue of the photocatalyst composite fibers E1 to E4 of Examples 1 to 4 is about 90.4% to 96.5%, and the total degradation rate of methyl orange is about 67.1% to 89.8%; Comparative Example 1~ The total degradation rate of methylene blue of fiber CE1~CE5 is about 47.6%~94.4%, and the total degradation rate of methyl orange is about 33.6%~70.4%, indicating that the photocatalyst composite fiber of the invention has high visible light degradation efficiency.

In summary, the photocatalyst composite nanofiber of the invention has the characteristics of small diameter, large specific surface area, high thermal stability and high visible light degradation efficiency by the synergistic action of titanium dioxide, graphene oxide and transition metal particles, which is beneficial to the photocatalyst composite nanofiber. The organic pollutants in the wastewater are adsorbed and transmitted by visible light, and can be obtained by a sol-gel method in combination with an electrospinning technique, so that the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

Claims (6)

The invention relates to a method for preparing a photocatalyst composite nanofiber, comprising the steps of: mixing a titanium-containing precursor, an organic polymer, a stabilizer and an organic solvent to obtain an initial solution; mixing the aqueous graphene oxide solution with the initial solution to obtain a host solution; mixing a transition metal ion and a chelating agent with the host solution and heating to obtain an electrospinning solution; and electrospinning the electrospinning solution to form a plurality of nanofibers. The photocatalyst composite nanofiber according to claim 1, wherein the weight ratio of the transition metal ion to the titanium-containing precursor ranges from 1:6000 to 500:6000, and the graphene oxide and the titanium-containing precursor are used. The weight ratio ranges from 0.0001:6000 to 500:6000. The photocatalytic composite nanofiber according to claim 1, wherein the transition metal ion is a silver ion. The photocatalyst composite nanofiber according to claim 1, wherein the organic polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinyl acetate, polyethylene glycol or pluronic. The photocatalyst composite nanofiber according to claim 1, wherein the stabilizer is acetic acid, and the chelating agent is an indigo dye. The photocatalytic composite nanofiber according to claim 1, wherein after the nanofibers are formed, a calcination step of heating the nanofibers is further included.