Friday, 6 December 2013

Catalytic Clothing: How Your Jeans Can Purify Air

by Emilie Bergstrӧm

The UK frequently falls short of meeting EU air pollution emission targets, and it is estimated that air pollution is responsible for 50,000 deaths in the UK each year. Nitrogen oxides, NOx, and volatile organic compounds (VOCs), both produced in massive quantities from motor vehicles and industry, are two of the most prominent classes of pollutants. NOx are known to cause and worsen respiratory diseases, such as asthma and emphysema, and some VOCs are known carcinogens.

It has been known for some time that the harmful NOx and VOCs can be removed from the atmosphere via a catalytic conversion. Nanosized particles of titanium dioxide, TiO2, or nano-titania, are powerful photocatalysts that use sunlight and oxygen to speed up the oxidation of NOx into water soluble nitric acid that can be washed away with the rain, while also converting VOCs into fatty acids and soaps. 

Up until recently, nano-titania catalysts have only been placed on hard surfaces such as the walls of buildings. Helen Storey and Tony Ryan wanted to explore new applications of this technology. They contacted Cristal Global, the second largest supplier of nano-titania, to suggest collaborating on an initiative involving textiles. It was discovered that the efficacy of the catalyst when applied to textiles, particularly denim, was far higher than anticipated.

They have now partnered with the ecological cleaning brand, Ecover, to create a fabric softener able to deliver the photocatalyst to the surface of any piece of clothing during washing. The active agent is packaged within a shell that is attracted towards, and binds to, the surface of the clothing during the wash. Daily wear and washing create no problem for the catalyst particles, and they do not fall off until the cotton fibres of the jeans eventually break.

The key to catalysis, and increasing the rate of removal of NOx, is a high surface area. Nanoparticles have an extremely high ratio of surface area to volume and a pair of jeans has a surface area greater than 195 square feet. It has been estimated that if one person wears Catalytic Clothing for one day, they could remove the same amount of NOx as is produced by the average family in one day. 

A common misconception is that Catalytic Clothing will be a ‘dirt magnet’, putting people at greater risk of exposure to pollutants. This is not the case – the technology won't actively attract any pollutants, but will break down anything that comes within very close proximity of the catalyst's surface.