From: Andy Soos, ENN
Published December 21, 2012 08:00 AM

NOx Removal with Paint

NOx is a pollutant that comes from all combustion emissions. It can be minimized but not eliminated at the stack. Painted surfaces (a very common urban surface area) with photo-catalytic characteristics may be able to clean the air of nitrogen oxides and other health-endangering substances. Using a new testing procedure, Fraunhofer researchers can find out how the coatings behave during a long-term test. They will introduce the new test at the booth of the Fraunhofer Building Innovation Alliance January, 2013, in Munich, Germany.


Technology to remove NOx has come a long way in the last 5o years but it does its best at smokestack industries and not automotive traffic.  So NOx levels have improved but more needs to be done. 

In the meantime, the European Union has tightened the limit values even further; in many areas these limits are being exceeded. Michael Hüben of the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg, Germany, knows that "on stretches with heavy traffic there is a particular need for action."

During the next two years, the Fraunhofer researchers want to examine the"Effectiveness of photo-catalytic removal of nitrogen oxide on coated building test panels".

Specifically this is how photo-catalytic surfaces contribute to the removal of NOx and how the coatings prove themselves during long-term operation. The process will be introduced at the 2013 BAU trade fair at the joint booth of the Fraunhofer Building Innovation Alliance.

"Coatings that are photo-catalytically active can help to reduce nitrogen oxides," explains Dr. Michael Hüben, "There are already a number of products available for the photo-catalytic coating of surfaces, but the measurement method standardized according to ISO 22197-1 cannot be applied to all problems. At the IME, we have now developed a special measurement cell which we are using in our project."

Prepared test samples will be measured at predetermined intervals in the measuring cell. Hüben explains the set-up of the test: "The surface of the test sample must be photo-catalytically active, meaning it removes NOx when exposed to light." The surfaces contain titanium dioxide catalysts, a material that is affordable and available in large quantities. Then, exposed to daylight, titanium dioxide catalyzes the nitrogen oxide into nitrate. "The photo-catalytic activities of the samples are determined using a flow-through process," says the scientist.

During the next two years, the experts will determine how much NOx is being removed by the coated surface. In this manner, they will obtain a basis for the long term effects of the coatings. If successful the houses and buildings in an urban area will be usable as a pollution control device.  This would make it possible to reduce the particle pollution in urban areas.

"Another area of application for the measurement process are interior rooms. Here, too, there are products commercially available that promise to improve air quality in interior rooms," explains Mr. Hüben’s colleague, Frank Neumann from the Fraunhofer Institute for Surface Engineering and Thin Films IST.

"Here, too, experimental measurements help us to work up standards and certifications and standardize existing test processes." 

For further information see Coatings.

Test Stand via Wolfram Scheible/Fraunhofer.

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