Clean building

A consortium of European firms in the chemicals and construction sectors are testing a range of building materials which will not only clean themselves, but might also eat environmental pollution.

UK-based Millennium Chemicals is among the companies involved, along with the European Commission's Joint Research Centre in Ispa, Italy.

The consortium is part of a project rejoicing in the name PICADA (photocatalytic innovative coverings applications for de-pollution assessment). This is developing a series of materials, including plaster, mortar, architectural concrete and coatings, which contain titanium dioxide particles.

Known as 'smart coatings', these materials use the photocatalytic properties of TiO2 to decompose oxides of nitrogen and volatile organic compounds that pollute city air. 'Smart coatings can cause a revolution, not only in the management of air pollution, but also in how architects and town planners tackle the persistent problem of urban smog,' comments Philippe Busquin, European commissioner for research.

The PICADA project, which began in 2002 and is scheduled to end next year, is costing a total of 3.4million Euros, of which 1.9million Euros is coming from the EC. It is part of the EC's efforts to reduce nitrogen oxide levels to under 21 parts per billion per year by 2010.

Currently, the researchers are testing a porous coating containing TiO2 nanoparticles and alkaline calcium carbonate. Pollutants are adsorbed onto the nanoparticles and are degraded by the light-triggered catalytic action of the TiO2, producing acidic by-products which are washed away by rain and neutralised by the calcium carbonate.