Water purification methods
Water purification methods available now work on the use of ultraviolet light or involve a suspension of nanoparticles. The ultraviolet light method is relying on a good source of UV light and in the other method suspended nanoparticles have to be recovered after the water purification process is over.
Zinc oxide nanorods
Zinc oxide nanorods have been used for destroying bacterial contaminated water. Nanorods grown on glass substrates and activated by visible light of solar energy have been found to be effective in killing both gram positive and gram negative bacteria by a team of researchers at the Asian Institute of Technology, Thailand. This discovery has immense possibilities for cheaper and environmentally friendly purification of water.
Principle
Deliberate defects are incorporated in ZnO nanorods grown on glass by creating oxygen vacancies and interstitials, which then allows visible light absorption. In the absence of light, ZnO dissolves slowly and releases zinc ions having anti bacterial properties to penetrate the bacterial cell envelope. This retards the growth of microbes, but under illuminated conditions the zinc ions get doubled due to photo catalysis and destroy the microbes. An electron degradation mechanism dominates the photo catalytic processes of ZnO material.
Benefits
Such ZnO nanorods have been tested on Escherichia coli and Bacillus subtilis bacteria and the working of this method under sun light instead of UV light has a higher potential for huge commercial application. The levels of zinc ions removed from the rods to the water are safe for human consumption according to the researchers.