CN106140129A - Metal-doped nano TiO2 photocatalyst and preparation method thereof - Google Patents

Abstract

The invention provides a method for preparing metal-doped nano- _TiO2 photocatalyst, the preparation method is as follows: add butyl titanate to absolute ethanol, add diethanolamine as an inhibitor, magnetically stir and disperse evenly, as reactant 1 Standby; add nitrate of metal ions in deionized water, add absolute ethanol after fully dissolving and mix evenly, and use it as reactant 2 for standby; while stirring, add reactant 2 to reactant 1 drop by drop at a certain speed to adjust the pH =4, stirred for 2 hours, aged for 12 hours to form a gel, and baked in a muffle furnace at 450-550° C. for 2.5 hours to obtain the photocatalyst. The results show that the catalyst prepared by controlling the dropping rate to 1 drop/4S when preparing the sol and controlling the temperature at 500°C during calcination has a good catalytic effect. The method has the advantages that the prepared catalyst has high catalytic efficiency for pollutants and the preparation method is simple.

Description

Metal-doped nano TiO2 photocatalyst and preparation method thereof

technical field

The invention belongs to the field of catalysts, in particular to a metal-doped nano _TiO2 photocatalyst and a preparation method thereof.

Background technique

In recent years, TiO ₂ photocatalytic technology has been widely studied in air treatment and sewage treatment, which has far-reaching significance for the sustainable development of the environment. However, nano-TiO ₂ powder and sol have defects such as low utilization rate of light energy in wastewater treatment, and are difficult to be practically applied in air purification because of the large polluted area. Modification of photocatalysts such as doping, acidification or coupling can appropriately broaden the response range of the catalyst to light and improve the utilization rate of the catalyst to light.

TiO ₂ can be divided into anatase type, brookite type and rutile type according to different crystal forms. Among them, the anatase type and the rutile type have a lot of similarities in structure, and both belong to the tetragonal crystal system. The difference lies in the connection mode and distortion level between the octahedral structures inside the two. This difference makes the mass density and energy band structure of rutile and anatase TiO ₂ different. The energy gap of anatase is 3.3eV, and the mass density is 3.9g/cm ³ ; the energy gap of rutile is 3.1eV, which is slightly lower. For anatase, the mass density is 4.2g/cm ³ . The high specific surface area of anatase TiO ₂ makes it have strong adsorption capacity, and the electrons and holes generated by light excitation are not easy to recombine, and the catalytic performance is high. Anatase is usually used as a photocatalyst for research.

Ion doping is to introduce an appropriate amount of other ions into the lattice of nano-TiO ₂ , causing surface defects or changes in crystallinity, thereby hindering the recombination of photogenerated electrons and holes, or red-shifting the absorption wavelength of nano-TiO ₂ , improving Its utilization rate of visible light improves its photocatalytic effect.

Contents of the invention

In order to solve the above technical problems, the present invention provides a simple and convenient method for preparing metal-doped nano- _TiO2 photocatalysts. Specifically include the following steps:

(1) Slowly add 19ml of butyl titanate into 50ml of absolute ethanol, add 27ml of diethanolamine as an inhibitor, stir magnetically for 1.5h to disperse evenly, and use it as reactant 1.

(2) Add nitrates of Zn ²⁺ , Cu ²⁺ , and La ³⁺ in the same mole percentage in 10 ml of deionized water. After fully dissolving, add 25 ml of absolute ethanol and mix evenly as reactant 2.

(3) While stirring, add reactant 2 to reactant 1 dropwise at a certain speed, adjust pH=4, and stir for 2 hours. Aged for 12 hours to form a gel, and baked in a muffle furnace at 450-550°C for 2.5 hours.

Further, the rate at which the reactant 2 is added dropwise to the reactant 1 is limited to 1 drop/4S.

Further, the temperature for calcining the gel in the muffle furnace is limited to 500°C.

Another aspect of the present invention provides a metal-doped nano- _TiO2 photocatalyst prepared by the above method.

Further, the metal doped in the nano- _TiO2 is Zn, and its doping amount is 0.15%, or the metal doped in the nano- _TiO2 is Cu, and its doping amount is 0.2%, or the The metal doped in nano-TiO2 is La, and its doping amount is 0.15%, or the metal _doped in nano- _TiO2 is La and Zn, and the doping amount of La is 0.1%, Zn The doping amount is 0.05%.

The advantages of the present invention are:

(1) The preparation method of the catalyst is simple and convenient; the catalyst itself is non-toxic, low in price, high in catalytic efficiency for pollutants, large in particle specific surface area, and high in removal rate of pollutants.

(2) The catalyst can degrade organic matter under normal temperature and pressure, decomposes thoroughly, does not produce secondary pollution, and has high application value.

Description of drawings

Figure 1 is the SEM image of nano- _TiO2 when the dropping rate is 1 drop/0.5S, 1 drop/2S, 1 drop/4S (from left to right).

Figure ₂ is the XRD pattern of nano-TiO2 at different calcination temperatures, where a (450°C), b (500°C), c (550°C) A is the anatase peak, and R is the rutile peak.

Figure 3 is the XRD pattern of Zn ²⁺ ion-doped nano-TiO ₂ at different calcination temperatures, where a (450°C), b (500°C), c (550°C), A is the anatase peak, and R is the rutile peak , E is the ZnTiO ₃ peak.

Figure 4 is the XRD pattern of Cu ²⁺ ion-doped nano-TiO ₂ at different calcination temperatures, where a (450°C), b (500°C), c (550°C), A is the anatase peak, and R is the rutile peak .

Figure 5 is the XRD pattern of La ³ + ion-doped nano-TiO ₂ at different calcination temperatures, where a (450°C), b (500°C), c (550°C), and A are anatase peaks.

Figure 6 is a diagram of the degradation rate of methyl orange by nano-TiO ₂ under different metal doping amounts.

Fig. 7 is a diagram of the degradation rate of metal-doped nano-TiO ₂ to methyl orange as a function of time.

Fig. 8 is a diagram of the degradation rate of methyl orange by La-Zn co-doped nano-TiO ₂ with time.

detailed description

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Example 1

Add 50ml of absolute ethanol to 19ml of butyl titanate and mix evenly, add 27ml of diethanolamine under medium-speed stirring, and magnetically stir for 1.5h, as reactant 1. Mix 10ml of deionized water and 25ml of absolute ethanol evenly as reactant 2. While stirring, reactant 2 was added dropwise to reactant 1 at the speed of 1 drop/0.5S, 1 drop/2S, and 1 drop/4S, respectively, and the pH was adjusted to 4. After stirring for 2 hours, let it stand still. A colorless transparent sol was obtained, which became a solid gel after aging for 12 hours, and the solid gel was roasted in a muffle furnace for 2.5 hours. The firing temperature is 450°C.

The obtained three kinds of nano- _TiO2 were analyzed by SEM, as shown in Fig. 1. It can be seen from the figure that the particle size and shape of the obtained product are also different with different dropping speeds. The faster the dropping speed, the easier it is to agglomerate during the formation of nano-TiO ₂ , and generate large particles with irregular shapes. When the dropping speed of reactant 2 When it is 1 drop/0.5S, the generated nano-TiO ₂ particles are coarse, uneven in size and low in dispersibility. Slow down the drop rate of the reactant 2, and the particle size of the product decreases. When the drop rate is 1 drop/4S, the nano-TiO ₂ is in the form of fine particles, which are uniformly dispersed and superimposed layer by layer.

Example 2

Slowly add 50 ml of absolute ethanol to 19 ml of butyl titanate, add 27 ml of diethanolamine under medium-speed stirring, and stir magnetically for 1.5 h to form a mixture 1. Mix 10ml of deionized water and 25ml of absolute ethanol evenly as reactant 2. While stirring, reactant 2 was added dropwise to reactant 1 at a rate of 1 drop/4S, adjusted to pH = 4, stirred for 2 h and then left to stand. A colorless transparent sol was obtained, which became a solid gel after aging for 12 hours, and the solid gel was roasted in a muffle furnace for 2.5 hours. The firing temperatures are 450°C, 500°C, and 550°C, respectively. Figure 2 is the XRD patterns of pure nano TiO ₂ obtained at three temperatures.

It can be seen from the figure that at 2θ=25.259°, 37.921°, 48.041°, 53.920°, 55.100°, 62.677°, 68.981°, and 75.037°, the TiO ₂ under the three temperature treatments of a, b, and c all appeared anatase The characteristic peaks of ore nano-TiO ₂ correspond to (101), (004), (200), (105), (211), (204), (116), (215) crystal planes respectively, indicating that 450 ° C, 500 The three kinds of TiO ₂ prepared at calcination temperature of ℃ and 550℃ all contain anatase nano-TiO ₂ , and there are no other diffraction peaks except anatase peak in a and b, indicating that a and b are all anatase nano-TiO _2. There is no rutile phase. Among the characteristic peaks of a and b, the peak height in b is more prominent, and the peak shape is sharper and clearer, indicating that the formation of anatase at 500°C is better than that at 450°C. In c, in addition to the above-mentioned anatase characteristic peaks that appear together with a and b, there are also characteristic peaks of rutile phases such as 27.421°, 36.060°, 41.260°, 44.041°, 56.658°, and 63.979°, indicating that the roasting temperature is 550°C , a part of the anatase phase nano-TiO ₂ transforms into the rutile phase.

Example 3

Dissolve zinc nitrate in 10ml of deionized water, add 25ml of absolute ethanol and mix well as reactant 1. Add 50 ml of absolute ethanol to 19 ml of butyl titanate, add 27 ml of diethanolamine as an inhibitor while stirring, stir for 1.5 h with magnetic force to disperse evenly, and serve as reactant 2. While stirring, reactant 1 was added dropwise to reactant 2 at a rate of 1 drop/4S, pH=4, and stirred for 2 h. Aged for 12 hours to form a gel, baked in a muffle furnace at 450°C, 500°C, and 550°C for 2.5h. The XRD patterns of nano-TiO ₂ doped with different ions at three firing temperatures are shown in Figure 3 (Zn ²⁺ /TiO ₂ ), Figure 4 (Cu ²⁺ /TiO ₂ ), and Figure 5 (La ³⁺ /TiO ₂ ).

As shown in Figure 3, anatase peaks appeared in the XRD patterns of Zn-doped nano-TiO ₂ a, b, and c prepared at three calcination temperatures, indicating that at 450°C, 500°C, and 550°C calcination temperatures, a , b, c produced anatase phase.

Among them, there are no other diffraction peaks except the anatase peak in a, indicating that the _TiO2 in a is all anatase phase. Among them, the diffraction peaks in b are basically anatase peaks, and a rutile peak appears at 2θ=50.022°. In addition, there are no diffraction peaks of ZnO and other zinc oxide phases, indicating that Zn ²⁺ basically enters the TiO ₂ crystal A corresponding solid solution is formed in the grid. From the peak shape and width, b is more prominent than a, and the trend between the peaks is clear, indicating that the crystallization status of doped nano-TiO ₂ is better than that of a. When the calcination temperature is 500℃, the rutile phase peak appears, indicating that the phase transition temperature of Zn ²⁺ /TiO ₂ from anatase to rutile is lower than that of undoped nano-TiO ₂ , indicating that ion doping can change the crystal lattice Elemental composition to change the phase inversion temperature.

Among them, at a calcination temperature of 550°C, a large number of rutile phases and ZnTiO ₃ phases appeared in c, and as the calcination temperature increased, nano-TiO ₂ transformed from anatase to rutile phase, and part of it transformed into ZnTiO ₃ , indicating that the calcination temperature was well controlled , is crucial for the preparation of doped nano-TiO ₂ .

Figure 4 is the XRD pattern of Cu ²⁺ doped nano-TiO ₂ prepared at 450°C, 500°C, and 550°C calcination temperatures. In the XRD pattern of Cu ²⁺ /TiO ₂ obtained under the following conditions, only anatase peaks appeared, indicating that the doped nano-TiO ₂ prepared at this temperature was a pure anatase phase, and the XRD of the product b obtained at a calcination temperature of 500 In the spectrum, rutile peaks appear at 2θ=27.519° and 69.003°, and as the temperature rises, anatase transforms into rutile. When the calcination temperature is increased to 550°C, the XRD pattern of the obtained product is shown in Figure c. In addition to the nano-TiO ₂ anatase phase peak in c, TiO ₂ appears at 2θ=27.382°, 35.585°, and 53.800° The diffraction peaks may be due to the doping of Cu ²⁺ and the continuous increase of calcination temperature, resulting in large-scale agglomeration of particles and the appearance of common phase TiO ₂ .

The calcination temperature ranges from 450°C to 500°C. As the temperature increases, the diffraction peak intensity of the calcination product decreases and the half-peak width increases. It may be that the increase in temperature will reduce the crystallinity of nano-TiO ₂ or cause grain refinement. Doping Afterwards, no characteristic peak of Cu was found in the XRD pattern, indicating that the preparation of doped nano-TiO ₂ by sol-gel method will make Cu ions evenly dispersed in the bulk phase of nano-TiO ₂ .

Compared with the XRD pattern of nano-TiO ₂ without Cu ²⁺ , it was found that the edge of the characteristic peak in the XRD pattern of nano-TiO ₂ doped with Cu ²⁺ showed a trend of broadening, and the peak shape was obviously not as clear as that of the undoped product. The increase of the intensity indicates that the doping of metal ions has a significant impact on the crystal form of nano-TiO ₂ , which may promote the transformation of nano-TiO ₂ crystal form, resulting in lattice defects, resulting in different degrees of broadening of the diffraction characteristic peaks.

Figure 5 is the XRD pattern of the product obtained by La ³⁺ ion-doped nano-TiO ₂ at 450°C, 500°C, and 550°C calcination temperatures respectively. , 53.893°, 55.104°, and 62.730° have anatase characteristic peaks, corresponding to crystal planes 101, 200, 105, 211, 204, and no other characteristic peaks appear, indicating that at 450°C, 500°C, 550°C At the calcination temperature, the anatase phase doped with nano-TiO ₂ was obtained, and no rutile phase and metal oxide phase appeared, indicating that La ³⁺ doping can inhibit the transformation of nano-TiO ₂ crystal form.

Comparing the XRD patterns of products at 450°C, 500°C, and 550°C calcination temperatures, it can be seen that with the increase of calcination temperature, the peak height of the characteristic peak of anatase decreases, and the diffraction peak broadens, such as 450°C, 500°C , the peak heights of the characteristic diffraction peaks around 2θ=25.275° at a calcination temperature of 550°C are 445, 365, and 264, respectively, and the peak heights of the characteristic diffraction peaks near 2θ=48.129° are 114, 60, and 57, respectively.

From the height of the peak shape, as the calcination temperature gradually increased from 450°C to 550°C, the peak height became lower and lower, indicating that the crystallization state tended to be imperfect as the temperature increased. From the perspective of peak width, as the calcination temperature increases, the sharpness of the peak shape decreases, and the peak shape tends to broaden, indicating that the grain diameter becomes smaller with the increase of temperature.

Example 4

Prepare several kinds of doping amounts respectively as 0.05%, 0.1%, 0.15%, 0.2%, 0.3%, 0.5% Zn ²⁺ /TiO ₂ , Cu ²⁺ /TiO ₂ , La ³ /TiO ₂ powders are reserved for future use (other The conditions are the same, the dropping rate is 1 drop/4s, PH=4, the calcination temperature is 450°C, and the time is 2.5h). A methyl orange solution with a concentration of 20mg/L was selected as the catalytic degradation object, and a 50W tubular ultraviolet lamp was used as the light source (the tube length was 30cm, and the diameter was 2.5cm). Weigh 0.5g of photocatalyst and add it into a beaker containing 350ml 20mg/L methyl orange solution. After mixing evenly by ultrasonication for 20 minutes, place the beaker in a closed box with a UV lamp. The distance between the mouth of the beaker and the bottom of the UV lamp is 15cm. Continuously carry out medium-speed magnetic stirring, take samples after 1 hour, and take the supernatant after centrifugation to measure the absorbance. The test wavelength of the ultraviolet-visible spectrophotometer is 465.2nm, and the degradation rate of methyl orange is calculated using the formula.

Figure 6 shows Zn ²⁺ /TiO ₂ , Cu ²⁺ /TiO ₂ , La ³⁺ /TiO ₂ and pure nano TiO ₂ The degradation rate of methyl orange under ultraviolet light for 1 hour. It can be seen from Figure 6 that the photocatalytic efficiency of doped nano-TiO ₂ is improved to varying degrees compared with pure nano-TiO ₂ , and the degradation rates of three metal-doped nano-TiO ₂ to methyl orange increase with the increase of metal doping amount. When the doping amount reaches a certain value, the photocatalytic activity is the highest, and when the metal doping exceeds the optimal doping amount, the photocatalytic activity shows a downward trend. The three kinds of metal ion doping all have an optimum doping amount, the optimum molar doping percentage of Zn ²⁺ in Zn ²⁺ /TiO ₂ is 0.15%, and the optimum molar doping percentage of Cu ²⁺ in Cu ²⁺ /TiO ₂ The molar doping percentage is 0.2%, and that of La ³⁺ in La ³⁺ /TiO ₂ is 0.15%. When the doping amount is the optimum ratio, the photocatalytic effect is the best.

Example 5

Weigh 0.5g each of pure nano-TiO ₂ , 0.15%-Zn ²⁺ /TiO ₂ , 0.2%-Cu ²⁺ /TiO ₂ , and 0.15%-La ³⁺ /TiO ₂ into 350ml 20mg/L formazan In the beaker of the base orange solution, after ultrasonication for 20 minutes, place the beaker in a closed box with an ultraviolet lamp, the beaker mouth is 15cm below the ultraviolet lamp, and the medium-speed magnetic stirring is continuously carried out during the experiment, and samples are taken every 20 minutes. The supernatant was taken to measure the absorbance, and the test wavelength of the ultraviolet-visible spectrophotometer was 465.2nm, and the degradation rate of methyl orange in different time periods was calculated by using the formula. The degradation rate of methyl orange with pure nano-TiO ₂ and three kinds of metal ion-doped nano-TiO ₂ under the optimal metal ion doping amount changes with time, as shown in Figure 7.

It can be seen from Figure 7 that the longer the degradation time, the higher the degradation rate of methyl orange, and the degradation rate of methyl orange doped with nano- _TiO2 is higher than that of pure nano- _TiO2 . properties can improve the photocatalytic efficiency of nano-TiO ₂ , when the degradation time is 2h, the degradation rate of 0.15%-La ³⁺ /TiO ₂ to methyl orange can reach 90%, and the degradation rate of 0.15%-Zn ²⁺ /TiO ₂ is 89%, 0.2%-Cu ²⁺ /TiO ₂ also reached 82%, excellent catalytic effect.

Example 6

Dissolve the combination of lanthanum nitrate and zinc nitrate with molar percentages of 0.05%-0.1%, 0.075%-0.075%, and 0.1%-0.05% respectively in 10ml of deionized water, add 25ml of absolute ethanol and mix well Then as reactant 1. Add 50ml of absolute ethanol to 19ml of butyl titanate, add 27ml of diethanolamine as an inhibitor while stirring, stir for 1.5h with magnetic force to disperse evenly, and use it as reactant 2. While stirring, reactant 1 was added dropwise to reactant 2 at a rate of 1 drop/4S, pH=4, and stirred for 2 h. Aged for 12 hours to form a gel, baked in a muffle furnace at 450°C for 2.5 hours before use.

Weigh 0.5g of La-Zn co-doped photocatalysts in different proportions and add them to a beaker containing 350ml of 20mg/L methyl orange solution. The distance between the mouth and the bottom of the ultraviolet lamp is 15cm. During the experiment, medium-speed magnetic stirring is continuously carried out. Samples are taken every 20 minutes. After centrifugation, the supernatant is taken to measure the absorbance. Degradation rate of base orange. The degradation curve of La-Zn co-doped nano-TiO ₂ to methyl orange is shown in Figure 8.

As can be seen from Figure 8, when lanthanum-zinc is co-doped, the degradation effect of doped nano- _TiO on methyl orange is different with the difference of lanthanum-zinc doping percentage. When the doping amount of lanthanum is 0.05%, the doping amount of zinc is At 0.1%, the degradation rate of methyl orange was 83% after 2 hours, which was lower than the single-doped photocatalytic efficiency of the two, indicating that the synergistic photocatalytic The effect is not reflected. When the doping amount of lanthanum is 0.1%, and the doping amount of zinc is 0.05%, the degradation rate of methyl orange reaches 95% after 2h, compared with the photocatalytic effect of single-doped nano- _TiO2 . It shows that doping nano-TiO ₂ with this co-doping ratio can properly improve its photocatalytic effect on methyl orange solution, reflecting the synergistic effect of metal ion co-doping.

In summary, the present invention describes the metal-doped nano-TiO2 photocatalyst and its preparation method, but the present invention is not limited thereto. Those skilled in the art should know that any changes and modifications can be made without departing from the scope of protection described in the claims of the present invention.

Claims (8)

1. prepare metal doping nano TiO for one kind₂The method of photocatalyst, comprises the following steps:

(1) butyl titanate is slowly added in dehydrated alcohol, adds diethanolamine and be uniformly dispersed as inhibitor, magnetic agitation, Standby as reactant 1；

(2) add the nitrate of metal ion in deionized water, add dehydrated alcohol mix homogeneously after fully dissolving, as instead Answer thing 2 standby；

(3) stir while reactant 2 is added dropwise in reactant 1 with certain speed, regulate PH=4, stir 2h, Ageing 12h forms gel, prepares metal-doped nano-TiO at Muffle kiln roasting 2.5h at 450～550 DEG C₂Photocatalyst.

Prepare metal doping nano TiO the most as claimed in claim 1₂The method of photocatalyst, it is characterised in that step (3) Described in reactant 2 is added drop-wise to the rate of addition in reactant 1 is 1/4S.

Prepare metal doping nano TiO the most as claimed in claim 1₂The method of photocatalyst, it is characterised in that step (3) Described in be 500 DEG C by gel in the temperature of Muffle kiln roasting.

4. a metal doping nano TiO₂Photocatalyst, it is characterised in that described photocatalyst is by arbitrary in claims 1 to 3 Method described in Xiang is made.

5. metal doping nano TiO as claimed in claim 4₂Photocatalyst, it is characterised in that described in be entrained in nano-TiO₂ In metal be Zn, its doping is 0.15%.

6. metal doping nano TiO as claimed in claim 4₂Photocatalyst, it is characterised in that described in be entrained in nano-TiO₂ In metal be Cu, its doping is 0.2%.

7. metal doping nano TiO as claimed in claim 4₂Photocatalyst, it is characterised in that described in be entrained in nano-TiO₂ In metal be La, its doping is 0.15%.

8. metal doping nano TiO as claimed in claim 4₂Photocatalyst, it is characterised in that described in be entrained in nano-TiO₂ In metal be La and Zn, the doping of described La is 0.1%, and the doping of Zn is 0.05%.