The paint that ate smog

Sydney Morning Herald
February 5, 2004

European scientists have devised a paint that soaks up nitrogen oxide gases emitted by vehicle exhausts, a pollution source that can cause smog and respiratory problems. The substance, Ecopaint, will go on sale next month and, when painted on the side of buildings, should be able to soak up nitrogen oxides (NOx) for five years until its novel coating is exhausted, New Scientist says.

The secret lies in spherical nanoparticles of titanium dioxide and calcium carbonate that are just 30 nanometres (30 billionths of a metre) across, mixed into a silicon-based polymer, polysiloxane.The particles are so tiny that the paint is clear, and pigment can be added to make the desired colour. The polysiloxane is relatively porous, and lets the NOx gases diffuse through it, so that they adhere to the particles of titanium dioxide.

The particles absorb ultraviolet radiation from sunlight, and the energy from this converts NOx in a chemical reaction to nitric acid, which is neutralised by the calcium carbonate, an alkaline. That produces "harmless quantities" of carbon dioxide, water and calcium nitrate, which wash away, the article, which is published in next Saturday's issue of New Scientist says.

The product was invented by a British company, Millennium Chemicals, under a European Union-funded program to help improve air quality in cities. An experiment conducted with a similar catalytic coating, which was painted on a stretch of road in Milan, Italy, in 2000, reduced levels of NOx at street level by 60 per cent, and residents reported they found it noticeably easier to breathe.

AFP

This story was found at: http://www.smh.com.au/articles/2004/02/05/1075853967536.html