Materials

Light-activated concrete scrubs air pollution out of traffic tunnels

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The new air-scrubbing concrete was tested in Banpo Underground Road Tunnel in Seoul, South Korea
Korea Institute of Civil Engineering and Building Technology
The new air-scrubbing concrete was tested in Banpo Underground Road Tunnel in Seoul, South Korea
Korea Institute of Civil Engineering and Building Technology
A diagram illustrating how the new air-purifying concrete works. A layer of titanium dioxide interacts with sunlight (or artificial light) to produce reactive oxygen species, which degrade air pollutants like nitrogen oxides, sulfur oxides, volatile organic compounds and ammonia into harmless end products
Korea Institute of Civil Engineering and Building Technology

Traffic is among the biggest sources of air pollution, but what if the very roads they drive on could help clear the air? Engineers in Korea have now demonstrated that photocatalytic concrete can help reduce pollution in tunnels.

While we need to transition to greener vehicles as soon as possible, it’s still going to take a few decades. In the meantime, finding other ways to slurp up that air pollution is important, so why not turn to the most common building material in the world to help? In recent years scientists have developed concrete that can convert some of the nasties in the surrounding air into harmless products.

These air-purifying concrete systems rely on a coating of titanium dioxide, which reacts to sunlight to produce molecules called reactive oxygen species (ROS). These have strong oxidizing power, which breaks down air pollutants like volatile organic compounds (VOCs), nitrogen oxides, sulfur oxides, and ammonia and prevents the formation of fine particulate matter.

In the new study, researchers at the Korea Institute of Civil Engineering and Building Technology (KICT) developed this kind of photocatalytic concrete and tested it in a traffic tunnel, where pollution is often higher due to poor air circulation. Artificial lights were installed along the walls to fuel the light-activated reactions in the concrete.

A diagram illustrating how the new air-purifying concrete works. A layer of titanium dioxide interacts with sunlight (or artificial light) to produce reactive oxygen species, which degrade air pollutants like nitrogen oxides, sulfur oxides, volatile organic compounds and ammonia into harmless end products
Korea Institute of Civil Engineering and Building Technology

The team found that levels of nitrogen oxides dropped by about 18% over 24 hours, and the end products of the reactions were salts, formed in part from the calcium content in the concrete. These salts were quickly washed away by rain. Better yet, the team says this process should allow the photocatalytic concrete to function indefinitely, without needing any extra maintenance beyond that of regular concrete.

The team plans to continue researching the technology to help get it commercialized and hopefully improve its effectiveness. Other examples have managed to reduce nitrogen oxide levels by 45%, or even an astonishing 70% when paired with graphene.

“Construction technology using photocatalysts can have an immediate effect on reducing fine particulate matter in the nation’s living environment” said Dr. Jong-Won Kwark, head researcher on the project. “We plan to build a system of cooperation with local governments and public corporations to expand trial demonstrations to other sites to achieve commercialization and distribution with practical effects.”

An earlier paper describing the photocatalytic concrete was published in the KSCE Journal of Civil and Environmental Engineering Research.

Source: KICT via Newswise

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5 comments
CarolynFarstrider
This needs a full Life Cycle Analysis, to see whether it is environmentally better than the alternatives, in terms of air pollution and carbon emissions. It's likely to be better to use electric vehicles, rather than trying to clean up emissions from dirty cars, as this technology does. We already have the electric vehicle tech, so why delay by trying to clean up and maintain fossil fuel emitters? Not all particulates are eliminated by using electric vehicles (dust is still generated from tyres and road surfaces, for instance) but the overall performance on gases is much better than diesel and petrol. I wonder if this research was funded by the oil and gas people?
Karmudjun
Michael - very good article. I wonder what the strength and durability of the concrete with titanium dioxide layer atop really is - if the calcium is leached from the concrete how long does it maintain its structural integrity? Other than that, unless someone is funding a complete ICE elimination drive to replace all "dirty cars" today, we need more of these adaptations that are decades late in development! The impact on human health and the global climate challenge will be one of many necessary immediate stop-gap measures, it is a shame they weren't investigated in the 1970's!

Not that anything would be different if these minimal impact detoxification steps had been implemented 50 years ago, we would still have the massive momentum of greenhouse gas driven climate change to halt and attempt to reduce the overall effects.
Drahcir Namdlog
Interesting that the concrete's developer seems to think that Nitric Acid (HNO3) and Sulphuric Acid (H2SO4) are, to quote the article, "harmless end products". Wouldn't want those "harmless end products" eating away at my vehicle's finish, or even worse, my body.
ljaques
Well, it's great to know that rain washes the "harmless byproducts" (nitric and hydrochloric acid) away, but the article title was about underground tunnels, where (usually anyway) there is no rain and not much sunlight.
ljaques
Correction: nitric and sulphuric acids.