The air in many major cities is so bad that it does not comply with EU air quality standards. Nitrogen oxides from car exhausts – and studded tires that tear up small particles – are some of the problems. Newspaper headlines in Sweden say that thousands die every year from air pollution.
The headlines are dramatic but it should be remembered that it is mainly people with heart, lung and vascular diseases that are affected. For healthy people, air pollution in major Swedish cities is not a major problem, but for people with heart and lung problems, the number of hospital admissions has increased. There is also reason to suspect that air pollution contributes to increased symptoms in asthmatic patients, affect lung growth in young children, and increase the frequency of lung cancer in the general population.
Econox™, a concrete product, from the company Starka, is now being tested in an urban environment and has shown to contribute to a decrease of nitrogen oxide (NOx) emissions.
Sunlight and titanium dioxide
“EcoNox ™ works with sunlight and acts as a catalyst to break down air-born nitrogen oxides. The concrete is made of titanium dioxide that catalyze the conversion of gaseous NOx into water-soluble nitrates. The nitrate salts are harmless and washed away when it rains,” says Björn Olsson, Marketing Director at Starka.
“In collaboration with the city of Malmö, we installed concrete slabs on the pavement of the busy Amiralsgatan. The result was that the levels of NOx fell by about 20 percent. This is equivalent to the emissions from every fifth car. Ongoing tests in Copenhagen also show good results.”
Titanium dioxide is a naturally occurring oxide of titanium (TiO2), a substance used as a white pigment in paints, for example, toothpaste and pharmaceuticals. The type of titanium dioxide most commonly used is Anastase and the particle size is on the nano-scale. EcoNox™ incorporates titanium dioxide in a special pigment in the top layer of the concrete, approximately 10 mm thick and the surface has the characteristics of a typical concrete slab. The photo-catalytic reaction that occurs cleans the air throughout the lifespan of the concrete.
It is the short-wave UV radiation in sunlight that initiates the photo-catalytic reaction, How effective the conversion of NOx to nitrates depends on environmental factors like humidity, air temperature and light intensity. The photo-catalytic reactions also break down organic dirt on the concrete surface.
Each manufactured batch of EcoNox™ is verified under the requirements of TX Active, which is a system of quality control and quality assurance of the photo-catalytic industry. EcoNox™ is registered in the Swedish construction industry Basta Records.
EcoNox ™ for several different products
“We are launching EcoNox™ in several other product categories. A facade element of a house can act as an air purifier and the retaining walls of concrete traffic circles could have the same characteristics. Another application is to provide manholes with EcoNox™ technology, and even ready-mixed concrete in parking areas for heavy vehicles can have air-purifying properties. The possibilities are endless,” says Björn Olsson.
The article was published in April 2013