Bridges, buildings and other concrete structures may soon be taking a large bite out of the air pollutants around them with a new photocatalytic coating being developed by researchers in Spain.
The coatings are based on nanoparticles that interact with sunlight and trigger a chemical reaction that disintegrates certain air pollutants, report the developers, led by a team at the UPNA-Public University of Navarre.
|The team behind Ecofotomat says its final product will be as paint-like as possible: able to be applied on site, affordable and weatherproof.|
The coatings are the result of the Ecofotomat project, a collaboration that began in 2010 involving the university, L’Urederra Technology Centre and the construction company Obras y Servicios TEX S.L.
L’Urederra manufactures and adapts the nanoparticles for use in coatings, and TEX provides the concrete and technical specifications for the building material. Spain’s Ministry of Education and Science and the European Regional Development Fund (ERDF) are also supporting the project.
The goal is to get the coating out of the lab and into actual service on a variety of construction materials and projects as soon as possible. The initial focus has been on a coating for concrete.
The team says the coating can reduce 90% of nitrogen oxides, 80% of hydrocarbons, and 75% of carbon monoxides to which it is exposed.
Reports of pollution-eating roof tiles, building wraps, pavement treatments and similar products have become widespread in recent years. But many of these are composite materials or clear sprays. The new coating, its developers say, is different.
“There are ceramics that have these types of coatings, but here we are working with concrete and with liquid solutions, because we want the final coating to resemble a paint as much as possible: one that can be applied on site, has a cost that is not too high, and is sufficiently tough to withstand the elements,” says researcher Javier Goicoechea.
He adds: “The good thing is that we are talking about very thin coatings of less than a micron (a millionth part of a meter) and which adapt very well to the profile of the material. For example, concrete is always very porous, and this coating will cause the whole porous surface to become active when the sunlight hits it.”
The coating can also degrade certain chemical compounds that become attached to the surface, thereby hampering the spread of bacteria and fungi. However, the mechanism is not like conventional antibacterial coatings that use a slow-release additive. Eventually, says Goicoechea, such coatings eventually run out of the antibacterial agent and the mechanism stops working.
|“Concrete is always very porous, and this coating will cause the whole porous surface to become active when the sunlight hits it,” says developer and industrial engineer Javier Goicoechea.|
“What we are talking about here is a material that has a built-in property: When the sunlight hits it, it produces free radicals on its surface that attack the air pollutants, specifically the monoxides and the nitrogen oxides.
“What we need to come up with is a matrix that is tough and permanent enough to immobilize those nanoparticles on the surface and which ensures that the coating remains in place—and all that at an affordable cost.”
Breaking Down Pollutants
The team has tested the coating by applying it over a bluish ink on concrete.
“When the concrete is exposed to the light, it is possible to see how the ink is destroyed on the area treated with the coating while remaining virtually intact on the remaining surface,” Goicoechea said.
“When the ink is broken down, we can estimate that when the light hits the surface, the coating acts and breaks down all the pollutants present in the air in the form of compounds attached to it.”
Although the coating is finished, the project has another year to run. Goicoechea would like to see it tested on a complete façade, to see how it works, ages and holds up to extreme climates.