Nanoparticles doubly strong
doi:10.1038/nindia.2011.132 Published online 19 September 2011
Researchers have produced a new nanocomposite that could be useful for disinfecting drinking water and detoxifying cyanide, a harmful chemical discharged into sewers by electroplating and metal finishing facilities.
Microbial contamination of surface water is potentially hazardous because such sources are tapped for drinking water. Although solar radiation can be used to disinfect water, this process takes around six hours. Other methods that use sulphur- or nitrogen-doped titanium dioxide require ultraviolet light. These take 90–120 minutes but are less effective than using solar radiation.
To find a fast and cost-effective alternative way of disinfecting contaminated water, the researchers prepared nanocomposites from nanoparticles of ZnO and TiO2. They used water containing lab-grown Escherichia coli bacteria as a biological indicator to evaluate the disinfection efficiency of the nanocomposite in the presence of artificial visible light and natural sunlight.
Working as a photocatalyst, the nanocomposite killed around 80% of E. coli bacteria in 30 minutes under visible light. The nanocomposite kills bacteria by binding nanocrystals to the bacterial cells. During the attachment process, harmful hydroxyl radicals flow from the irradiated nanocomposite to E. coli, thus inhibiting bacterial growth.
The nanocomposite also demonstrated the ability to detoxify cyanide under visible light and degrade dyes under ultraviolet light.
"The removal of cyanide and disinfection of bacteria using only recoverable and reusable cheap nanoparticles with air and natural sunlight is a significant development," says lead researcher C. Karunakaran. This finding offers a cheap way of providing safe, potable water, he adds.
The authors of this work are from: Department of Chemistry, Annamalai University, and Division of Microbiology, Rajah Muthiah Medical College, Annamalai University, Annamalainagar, Tamilnadu, India.