Alcoa announces “smog-eating” architectural panels

Titanium dioxide is really rather useful

Last week that giant multinational of aluminum production Alcoa announced its new “smog-eating” architectural panels – in other words cladding stuck to a building’s exterior that can remove pollutants from the surrounding air. The aluminum panels, branded Reynobond with EcoClean technology, have a titanium dioxide coating which breaks down pollutants in direct sunlight.

Of course the purifying properties of titanium dioxide are well known, and have been widely applied, both in so-called self-cleaning applications, such as an experimental cotton treatment; and products such as lightbulbs that purify the air in a room. We’ve even seen research products to apply titanium dioxide, also known as titania, to water purification systems.

Titanium dioxide is really rather useful. Because of its brilliant whiteness, the naturally-occurring compound is commonly used as a pigment in paints, plastics and papers, as well as food and medicines. Added to skimmed milk, it’s thought to increase palatability. Its ability to absorb ultraviolet radiation make it a commonly used ingredient in sunscreen.

But its titania’s photocatlaytic abilities under ultraviolet light that single it out for use in this and similar products. In fact, with the addition of tungsten trioxide or nitrogen ions, titania can act as a photocatalyst under visible light too. Titania is hydrophyllic, as opposed to hydrophobic, so that when used as a self-cleaning material, it is not wholly reliant on water to remove dirt. Instead, organic pollutants are broken down into “harmless matter” when exposed to light, oxidized by free radicals generated by the titania. The remaining matter is simply washed way come the next rainfall.

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via Gizmag – 

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‘Smog-eating’ material breaking into the big time

Titanium-dioxide-sample

Image via Wikipedia

1,000 square metres of the coated panels eat up the equivalent NOx output of four cars

 
What material can you find in toothpaste, sunscreen, solar cells, on the baseline at Wimbledon, in a Roman church, and along a tunnel in Brussels?

Full marks if you guessed titanium dioxide, a nearly ubiquitous but wholly unsung material.

Its brilliant white has made it a staple in pigments – hence Wimbledon – but its eco-credentials are still coming to the fore.

Titanium dioxide does a couple of clever tricks that mean we may well be seeing a lot of it in the future: it’s self-cleaning, and it breaks down pollutants in the air.

And the fact that thin films of it are clear is the reason that a number of manufacturers use it in glass applications such as skylights.

Paving the way

The self-cleaning aspect comes about because one processed form of titanium dioxide is what is called superhydrophilic – literally, “water-loving”, which means that when water hits a dirty titanium dioxide surface, that surface will draw in a whisper-thin sheet of water across its whole surface, displacing grime that then washes neatly away.

But its second trick of removing pollutants is what has made it an increasingly popular choice for environmentally-minded building projects.

A bit of the ultraviolet light in sunlight frees up electrons from the material, creating “free radicals” that actively break down pollutants including so-called NOx gases (molecules of varying proportions of nitrogen and oxygen) or VOCs (volatile organic compounds).

A number of pilot projects around the world have seen the material used in, for example, concrete – hence the Jubilee Church in Rome. In Japan, Mitsubishi markets a brand of titanium dioxide-treated paving stones and Toto makes coated ceramic tiles.

The material hit the news again this week when the aluminium firm Alcoa announced its new product Ecoclean, a titanium dioxide coating on aluminium panels for cladding buildings.

The firm claims that 1,000 square metres of the coated panels eat up the equivalent NOx output of four cars.

“What we see, especially in Europe, is more and more legislation… about the air quality in cities, and I think that Ecoclean is a product that can really help mitigate the effects of emitters such as cars by its air-cleansing characteristics,” Alcoa spokesman Jasper Van Zon told BBC News.

Ecology of scale

The fact that such a large manufacturer has joined the ranks could mean that the real-world use of the material can finally be assessed on a large scale, says Anne Beeldens of the Catholic University Leuven in Belgium.

Dr Beeldens has been working with colleagues for years to establish, with rigorous experiments, the full scope of titanium dioxide’s effects in a built environment.

“We were really sceptical when we started with this, but it really works on the extraction of pollutants out of the air,” she told BBC News.

“The problem is that you have so many parameters that it’s sometimes hard to prove it. We got some promising results in the lab, but it was still in the lab; I think now it’s all shifting to real applications.”

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