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Developed a method for purification of water with light


Disinfect water ordinary light learned experts from the University of Illinois. With this new technology allows the installation to continue its good work even after lighting.
The water is disinfected in many ways: by passing through a filter system (sometimes unusual), chlorinating, irradiating UV, using banal boiling. Ultraviolet light, for example, is used very often (from pool cleaning systems to portable devices for tourists), since it is known that ultraviolet rays kill microorganisms.
Jian Ku Shang and his Chinese colleagues from the Shenyang National Laboratory of Materials have developed a photo catalyst, which quickly and effectively disinfects water even under the rays of the visible spectrum. For a start, scientists doped fiber titanium oxide with nitrogen (so they can absorb visible light). Give compound TiON, which itself can kill the bacteria, but not very effective. Further chemical added in nanoparticles of palladium oxide (PdO).

It turned out that this addition significantly increased the effectiveness of disinfection. Solution, which contained a large number of bacteria E. coli, just covered the usual halogen table lamp (varying the exposure time). An hour later, the concentration of microorganisms decreased from ten million cells per liter to one cell in ten thousand liters.

The researchers then examined what happens to the solution in the dark (after turning off the lights). To do this, a vessel of water covered the first 10 hours, then turn off the light and see how goes further disinfection. It was found that even after 24 hours photocatalyst continued to kill E. coli.

Appeared, palladium oxide increases the effectiveness of disinfection in two directions at once. Photons falling on the surface TiON, form electron are whole pairs. In this charged holes react with water to give life hydroxyl radicals, and they in turn attack bacteria.


PdO nanoparticles takes over the remaining electrons, resulting in the latter can not connect to the holes and thus neutralize them. Moreover, these nanoparticles are transformed into another chemical state, while maintaining a negative charge. After turning off the light, electrons are released gradually, forming new water-oxidizing agents.

“It would be interesting to try to move the work of traditional photo catalysts in the visible light region. Indeed if you think about in the solar spectrum, only 5% and 46% of UV-visible light,” – says not involved in this study, Alexander Orlov, a professor at Stony Brook University, writes membrane. Such plants would use the energy from sunlight more efficiently. And the water in the room can be disinfected using fluorescent lamps.