Arbejdsrapport fra Miljøstyrelsen 32/2006 – Fotokatalytisk omsætning af NOx på beton

Fotokatalytisk omsætning af NOx på beton

Summary and conclusions

The outdoor air in the streets of Copenhagen and in other large cities is polluted with nitrogen oxides from traffic. The concentration of nitrogen oxides in the exhaust fumes from traffic has decreased during recent years, mainly due to the widespread use of catalytic converters in the exhaust systems of cars. However, the atmospheric concentration of nitrogen oxide at street level is still relatively high. In terms of public health nitrogen dioxide is the most interesting of the nitrous oxide gases since nitrogen dioxide can damage the lungs and their resistance to infections.

The purpose of this investigation is to verify if concrete with added titanium dioxide is able, by way of a photocatalytic reaction, to degrade nitrous gases in the air which come into contact with the surface of the concrete.

In this investigation the degradation of nitrogen dioxide is tested on concrete with and without added titanium dioxide, and the tests indicate that the photocatalytic degradation is limited. Furthermore, the tests indicate that also ordinary concrete without any titanium dioxide and also in complete darkness will absorb/degrade nitrogen dioxide.

It is possible that concrete that contains titanium dioxide does catalyze the oxidation of nitrogen monoxide into dioxide when radiated with ultraviolet light. However, this mechanism has not been investigated in this project.