CN1593748A

CN1593748A - Process for preparing titanium dioxide membrane photocatalyst

Info

Publication number: CN1593748A
Application number: CN 200410025754
Authority: CN
Inventors: 张金龙; 尤先锋; 陈锋; 田宝柱; 孙健
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2004-07-05
Filing date: 2004-07-05
Publication date: 2005-03-16

Abstract

The invention relates to a kind of manufacturing method of titanium dioxide photocatalyst, especially also relates to a manufacturing method of titanium dioxide photocatalyst through surface modification. Using chemical precipitation, get some titanium dioxide powder to dip in silver-ammonia solution. Then add oxydol for the reducing reaction. After the reaction, wash it and make it desiccate by certain time in the certain temperature. Finally, the titanium dioxide photocatalyst with silver loading can be acquired.

Description

Preparation method of titanium dioxide photocatalyst

Technical Field

The invention relates to a preparation method of a titanium dioxide photocatalyst, and particularly relates to a preparation method of a titanium dioxide photocatalyst subjected to surface modification.

Technical Field

The titanium dioxide photocatalytic material has wide application prospect in the fields of degradation of organic pollutants, sterilization, disinfection, purification of water and air and the like, thereby arousing the attention of governments and academic circles of various countries in the world. In recent years, there have been more and more papers and patents on titanium dioxide, and thousands of papers are published each year. In practical application, titanium dioxide has been used in the fields of water and air purification, self-cleaning of glass surfaces, antibacterial ceramic materials and the like, and great economic, environmental and social benefits are generated.

The titanium dioxide has the following main defects in practical application: (1) the photo-generated electrons and holes have short service life and high recombination rate, so that the quantum yield is low and the photocatalytic activity is not high. (2) The titanium dioxide has a wide band gap, and the exciting light is limited to an ultraviolet light region with the wavelength of less than 387nm, so that the utilization of visible light is limited. These factors limit the large-scale industrial application of titanium dioxide.

To enhance the activity of titanium dioxide, surface loading with noble metals is a viable approach. After the noble metal is loaded on the surface of the titanium dioxide, because the metal and the titanium dioxide have different Fermi levels, when the two materials are connected together, electrons can continuously migrate from the titanium dioxide to the metal until the Fermi levels of the two materials are equal. Noble metal is loaded on the surface of titanium dioxide serving as a catalyst, namely a short-circuit microbattery taking titanium dioxide and silver as electrodes is formed on the surface of the titanium dioxide, organic matters in liquid are oxidized by photoproduction holes generated by the titanium dioxide electrode, and photoproduction electrons flow to a metal electrode to reduce oxidation state components in the liquid phase, so that the recombination rate of the electrons and the holes is reduced, and the activity of the catalyst is improved.

Water Research Vol 25, NO.7, 823-827, 1991 reports reduction of silver nitrate adsorbed on the surface of titanium dioxide with sodium carbonate followed by calcination at 400 ℃ for 6 hours to obtain a silver-supported photocatalyst. The Journal of Catalysis168, 117-120, 1997 reports the loading of silver on titanium dioxide by photoreduction. The first method requires calcination to decompose silver carbonate or silver oxide into metallic silver supported on the surface of titanium dioxide, and since calcination at high temperature causes not only sintering agglomeration of silver particles on the surface of titanium dioxide but also agglomeration of titanium dioxide particles, which lowers the photocatalytic activity of titanium dioxide. The second method requires ultraviolet irradiation for 16 hours, which is long, and the long-term ultraviolet irradiation also causes agglomeration of silver particles on the surface of titanium dioxide. This indicates that both of these loading methods, while feasible, are problematic and require improvement.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a very simple and effective method for enhancing the photocatalytic activity of titanium dioxide and loading silver. The method uses hydrogen peroxide to reduce silver, the reducing agent is oxidized into water and oxygen, and no other organic matter is introduced in the reaction process, so that calcination is not needed, and silver agglomeration is avoided. And secondly, the reaction temperature is low, so that the silver particles are prevented from growing on the surface of the titanium dioxide under the high-temperature reaction condition. In addition, the reaction time is short, the target product can be obtained only by washing and low-temperature drying after the reaction is finished, and the related equation is as follows:

the experimental protocol was as follows:

soaking a certain amount of titanium dioxide powder in a silver ammonia solution, then adding hydrogen peroxide to carry out reduction reaction, washing after the reaction is completed, and drying at a certain temperature to obtain the silver-loaded titanium dioxide photocatalyst.

The silver-ammonia solution can be prepared from silver nitrate and ammonia water, and can also be prepared from silver nitrate, ammonia water, potassium hydroxide or sodium hydroxide.

The impregnation conditions are as follows: the soaking time is 0.25-2 hours, the temperature is 0-40 ℃, and the pH value is 8-14. Preferred impregnation conditions are: the dipping time is 0.5-1 hour, the dipping temperature is 20-30 ℃, and the pH value is 9-12.

The drying temperature is 40-100 ℃, the drying time is 1-12 hours, the preferred drying temperature is 60-80 ℃, and the drying time is 3-8 hours.

The silver loading method is also suitable for other semiconductors, such as zinc oxide, cadmium sulfide, aluminum oxide, silicon oxide, tin oxide and the like.

The photocatalytic activity characterization of titanium dioxide is carried out by degrading an aqueous solution of methyl orange under ultraviolet light, and the experiment is carried out at normal temperature and normal pressure. The experimental steps are as follows: accurately weighing 0.05 g of silver-loaded titanium dioxide powder, and adding the silver-loaded titanium dioxide powder into 50mL (40mg/L) of methyl orange solution; followed by sonication for 10 minutes and pre-adsorption in the dark for 30 minutes. Then starting an ultraviolet lamp for irradiation, carrying out photodegradation reaction, taking a sample every 30 minutes, measuring the absorbance at the maximum absorption wavelength under an ultraviolet-visible spectrophotometer, calculating the degradation degree according to the corresponding relation of the absorbance and the concentration, and comparing the photocatalytic activity of the catalyst.

Drawings

Fig. 1 is XRD patterns of the catalyst with silver supported (silver supported at 1%, 2%, 4% by mass, respectively) and the catalyst without silver supported.

Fig. 2 is a schematic diagram of the photocatalytic activities of the silver-supported (silver-supported mass percentages of 1%, 2%, and 4%) catalyst and the silver-unsupported catalyst.

Fig. 3 is a TEM image of the catalyst loaded with silver (silver loading mass% 2%, respectively).

Detailed Description

Example 1

Weighing 0.9ml of silver nitrate aqueous solution (0.05mol/L) and ammonia water (30% volume ratio) until the pH value is 8 to obtain silver ammonia solution, soaking 0.5 g of titanium dioxide powder in the silver ammonia solution at 0 ℃ in ice water bath for 20 minutes, and adding 0.3ml of hydrogen peroxide (2% volume ratio) to perform reduction reaction, wherein the theoretical loading capacity of silver is 1%. After 1 hour of reaction, the powder was washed and dried at 50 ℃ for 12 hours.

Example 2

Measuring 1.87ml of silver nitrate aqueous solution (0.05mol/L) and ammonia water (30% volume ratio) until the pH value is 8, continuously dropwise adding sodium hydroxide (0.1mol/L) until the pH value is 10 to obtain silver ammonia solution, soaking 0.5 g of titaniumdioxide powder in the silver ammonia solution at 25 ℃ for 45 minutes, adding 0.6ml of hydrogen peroxide (2% volume ratio) for reduction reaction, washing the powder after the reaction is carried out for 1.5 hours, wherein the theoretical loading capacity of silver is 2%. Dried at 80 ℃ for 4 hours.

Example 3

Weighing 3.74ml of silver nitrate aqueous solution (0.05mol/L) and ammonia water (30% volume ratio) until the pH value is 8, continuously dropwise adding potassium hydroxide (0.1mol/L) until the pH value is 10 to obtain silver ammonia solution, soaking 0.5 g of titanium dioxide powder in the silver ammonia solution at 40 ℃ for 60 minutes, and adding 1.2ml of hydrogen peroxide (2% volume ratio) to carry out reduction reaction, wherein the theoretical loading capacity of silver is 4%. After 2 hours of reaction, the powder was washed and dried at 60 ℃ for 12 hours.

The XRD of fig. 1 clearly shows that the peak with zero-valent silver appears, most clearly at 4% loading; as can be seen from a comparison of the degree of degradation of methyl orange over two hours on fig. 2, examples 1, 2 and 3 all showed a significant increase in photocatalytic activity over the unsupported sample, with 2 being more than doubled. The larger circular black particles in the TEM image of fig. 3 are elemental silver particles with a diameter of about 30 nm.

Claims

1. A process for preparing the photocatalyst of titanium dioxide by chemical deposition method includes such steps as immersing a certain amount of titanium dioxide powder in the solution of silver ammonia, adding hydrogen peroxide for reduction reaction, washing, and drying at a certain temp for a certain time.

2. The method as set forth in claim 1, wherein the silver ammonia solution is prepared from silver nitrate and ammonia water, or silver nitrate, ammonia water, potassium hydroxide or sodium hydroxide.

3. The method of claim 1, wherein said impregnation conditions are: the soaking time is 0.25-2 hours, the temperature is 0-40 ℃, and the pH value is 8-14.

4. A process according to claim 3, characterized in that the impregnation conditions are preferably carried out for an impregnation time of 0.5 to 1 hour, at an impregnation temperature of 20 to 30 ℃ and at a pH of 9 to 12.

5. The method as set forth in claim 1, wherein the certain temperature is 40-100 ℃ and the drying time is 1-12 hours.

6. The method according to claim 1, characterized in that the temperature is preferably 60-80 ℃ and the drying time is 3-8 hours.