Photocatalysis, the technology that offers a break from pollution


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The word photocatalysis It is still quite unknown to many, although this technology has been used in Spain for quite some time. However, now is when it is booming. The process of photocatalysis mimics that of photosynthesis that plants do, but in this case solar energy is captured to convert it into chemical energy. There are many applications, including the improvement of ambient air quality and water purification.

Photocatalysis is a photochemical reaction and as you remember Daniel Gonzalez Munozdoctor in Photocatalysis from the UAM: "At the beginning of the 20th century, scientists tried to imitate the photosynthesis process of plants, but it was left in the background compared to oil and coal."

With the oil crisis of the 1970s, the situation changed and this process began to be taken into account, which has been applied to different fields. More than 20 years ago, for example, its effect on the degradation of pollutants in the air began to be studied in Japan.. "In Spain it is very established at an industrial level, there are already many companies with construction materials to degrade air pollutants, such as viruses and bacteria," he clarifies.

For photocatalysis to occur, a photocatalyst, «molecules that absorb light energy and transmit it to another molecule. At an industrial level, most photocatalysts are based on titanium dioxide," adds González.

"Spain began to be interested in this technology in the year 2000 and the first application that was carried out was in a section of Martín de los Heros street in Madrid, through the City Council," he says. David Almazan, president of the Iberian Association of Photocatalysis. It was something new, it started to sound good and Barcelona made the first applications in buildings, pavements and sidewalks. «Private companies, for CSR reasons, apply it in car parks, health centers... Interest grows and more companies proliferate", Add. From this non-profit association that unites manufacturers, technology centers, architecture studios, engineering and universities, among other entities, they assure that "since last year there has been a greater interest in this technology that tries to improve the lives of citizens. Especially indoors because more than 90% of the time we were in confined areas.

Applications

In recent years, more and more manufacturers are using this technology in their products, and we already find paints, cement, building covers, paper or fabrics that include photocatalysts. Prices are becoming more competitive, although they can be up to 20% more expensive than a similar material without these characteristics. "It is a technology that needs to constantly advance, it has an infinite path, the efficiencies are good, but they can be much better," admits Almazán. Desktop photocatalysis devices are already on the market, which are plugged in and clean the air. There are also advances with fabrics, "you can be fashionable by decontaminating the world", and work is being done on the application of this technology on surfaces such as rubber for playgrounds, collaborating in their disinfection.

Last year, for example, the company sundisafrom the digital printing sector, displayed in Madrid and Barcelona advertising banners that received the Pureti treatment, reducing pollution by eliminating polluting elements. A post printing technique that purifies the air through photocatalysis.

The Covid has helped to develop more quickly the whole part of air quality improvement, “because the market demands it. It helps clean the air and kills viruses." Indoors, the most efficient way is to place the photocatalyst in the air conditioning ducts, which are very few accessible. "A device is placed inside the duct so that when the air circulates it is cleaned and the air that re-enters is cleaner," he points out. Outdoors, there is a wide variety of products to apply to sidewalks, building cladding, roofing or even advertising banners.

Of course, we must bear in mind that “it does not make the contamination disappear. It is a plugin that can make sites safer and cheaper within the construction. And it is a way of harnessing the energy of light”, says Daniel González.

Although the use of photocatalysis in industry is already widespread, in the field of research there are still many challenges ahead. The UAM researcher recalls that titanium oxide has a drawback: «Absorbs in the ultraviolet range of the solar spectrum, which is only 5%». It would be necessary to modify the titanium oxide to be able to absorb more light and thus achieve more efficient processes. Another challenge will be to achieve “photocatalysts that are more durable”.

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