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Smart paper can clean dirty air

Researchers at RISE have developed a paper containing zinc oxide. The paper has electrical properties and may be a future solution in the fight against air pollution.

Zinc oxide is not solely an ingredient in sunscreens, it can also be used in paper manufacture to make paper photoconductive. This means that paper is able to conduct electrical current when exposed to light.

“By allowing air to stream over the conductive paper, while simultaneously exposing it to UV light, it is possible to break down dirt and particles,” explains Karl Håkansson, senior research associate in the field of bio-based electronics at RISE.

He goes on to explains that the technique is based on the photocatalytic characteristics of zinc oxide. 

“This means that zinc oxide stimulates the formation of free radicals when exposed to UV light. These free radicals can then break down various elements and particles. UV light in itself is also used for its germicidal qualities; however, photocatalysis reinforces this effect.

Cheap method to clean air

There are currently a number of air cleaning methods available but the advantage of zinc oxide is that it is in plentiful supply and the new zinc-oxide paper is cheap to manufacture in large amounts. If costs can be held down, it will also be possible to build photocatalytic reaction chambers. Dirty air can be passed through these chambers through a long column and across the illuminated paper. Photocatalysis does produce certain potentially harmful byproducts but as long as the column is sufficiently long it is possible to ensure that these are completely broken down so that they don’t diffuse. Another advantage of the paper is the size of the particles.  

“The zinc oxide particles in our paper are in the microscopic range. Photocatalytic air filters often use potentially hazardous nanoparticles; however, our filter does not include particles this small,” explains Mats Sandberg, another member of the research team behind the technique.

Can be used in urban areas

The paper filter has been developed by researchers at RISE in collaboration with Linköping University. It is yet to be commercialised, although the hope is that it will have applications in cleaning the atmosphere in urban areas with poor air quality, for example Chinese cities. Another specific area of use is purifying air of greenhouse gases other than carbon dioxide, for example methane.

“In theory, I can see no reason why the filter shouldn’t be ready for use fairly soon. The difficult lies in making the technology available in those areas where it is most needed. We have a good concept and now we would like to identify opportunities and collaborations in countries where it is needed and can be put to use,” concludes Mats Sandberg.