Titanium IN interior paint – photocatalysis process and viruses

But what is photocatalysis really? What are photocatalysts?  

These questions were answered by prof. Ph.D. engineer Antoni Morawski from the Department of Inorganic Chemical Technology and Environmental Engineering at the West Pomeranian University of Technology in Szczecin.

– According to the definition – photocatalysis is a change in the rate of a chemical reaction or its initiation under the action of ultraviolet and/or visible radiation in the presence of a substance (photocatalyst) that absorbs the radiation and enables the oxidation-reduction chemical reaction to take place on the surface, e.g. between oxygen from the air and adsorbed contaminants, which may also be pathogenic microorganisms. Hydroxyl radicals generated on the photocatalyst surface have a higher oxidation potential than ozone, which is important for disinfection.

Is this a new discovery? Maybe it hasn't been checked enough yet?

– The ability of titanium dioxide (TiO 2 ) to act as a photocatalyst has been known for several decades (1921 to be precise). But this feature was not appreciated much for many years. Interest in using the photocatalytic properties of TiO 2 re-emerged when a paper on photoelectrolysis of water was published by Fujishima and Honda in 1972. This activity was soon used both for the oxidation of pollutants, wastewater treatment, drinking water purification, and water treatment for industrial vegetable washing. Titanium dioxide-coated filters were used to disinfect the air. Many subsequent studies have demonstrated the usefulness of photocatalysis for water disinfection, including the destruction of bacteria. Potential capabilities to destroy cancer cells have been discovered. However, what is new is the use of the advantages of TiO 2 in paint coatings.

What about viruses? Now this is such a topical topic.

– There have been a lot of publications on this topic recently. For example, in their work Photocatalytic inactivation of influenza virus by titanium dioxide thin film, the Japanese demonstrated the inactivation of the influenza virus by photocatalysis using TiO ₂ (R. Nakano, H. Ishiguro, Y. Yao, J. Kajioka, A. Fujishima, K. . Sunada, M. Minoshima, K. Hashimoto, Y. Kubota - "Photochemical and Photocatalytical Science", 2012).

Similarly, in the work Extermination of influenza virus H1N1 by a new visible-light-induced photocatalyst under fluorescent light (Sei-Young Choi Bongrae Cho - "Virus Research", 2018), it was confirmed that the photocatalyst based on TiO ₂ with the addition of transition metals (iron , magnesium and manganese) showed antiviral activity against the H1N1 influenza virus. During testing, the virus was eliminated by over 99% within 30 minutes. As stated - " it would be desirable to use this photocatalyst for disinfection to reduce the transmission of the virus through droplets and aerosols, as well as through surface contact ." E.A.A.Kozlov et al. in the publication Inactivation and Mineralization of Aerosol Deposited Model Pathogenic Microorganisms over TiO ₂ and Pt/TiO ₂ (Environmental Science and Technology, 2010, 44, 512-51-26) proved that on pure TiO ₂ after 30 minutes of irradiation with radiation UVA results in 90% inactivation of the influenza A (H3N2) virus, and on TiO ₂ modified with platinum - 99.8% inactivation of this virus.

Extensive research in another work was also carried out by R. Nakano, M. Hara, H. Ishiguro, Y. Yao, T. Ochiai, K. Nakata, T. Murakami, J. Kajioka, K. Sunada, K. Hashimoto, A. Fujishima , Y. Kubota ( Broad Spectrum Microbicidal Activity of Photocatalysis by TiO ₂ – Catalysts, 2013). Among others studied Gram-positive bacteria, e.g., methicillin-resistant Staphylococcus aureus vancomycin-resistant Enterococcus faecalis Streptococcus pneumoniae , which were readily inactivated by photocatalysis, while some Gram-negative bacteria, e.g., Escherichia coli and Pseudomonas aeruginosa were resistant to many drugs were deactivated gradually. Influenza virus (enveloped virus) and feline calicivirus (non-enveloped virus) were also inactivated during the tests.

The above research (and many others) clearly confirm that photocatalysts are an effective method against many harmful pathogens, and intensive work in this direction is underway around the world.

You mentioned that painted walls can help protect your health? Isn't this a mistake?

– Surfaces contaminated with microorganisms pose a threat to people living among them. Dust mites, bacteria, viruses and molds accumulate on walls and furnishings. This results in asthma, allergies and infections. This applies to both residential premises and healthcare facilities. A wealth of information available in the literature demonstrates the effectiveness of photocatalytic TiO ₂ in deactivating a variety of microorganisms, including bacteria, viruses, fungi and yeast.

Infectious diseases caused by antimicrobial-resistant bacteria are becoming one of the main problems in the use of antibiotics worldwide. The survival of these microorganisms on medical surfaces and devices leads to the transmission of nosocomial diseases. Nosocomial pathogens are believed to contribute to many deaths.

Many advanced technologies are being developed around the world to reduce the microbial burden in hospital environments. New strategies to prevent related infections are constantly evolving, including: hygiene procedures using new liquid biocides or touchless technologies, coating disinfection surfaces with metals (copper, silver) or light-activated catalysts such as TiO nano-particles ₂.

Challenges related to infections in healthcare and the increase in the spread of antimicrobial-resistant bacteria engage scientists in researching this field of nanotechnology and photocatalysis as a new source of improving hospital hygiene.

It has also been found that materials that are inert in their basic form are reactive when present in the form of nano-particles, and in the case of titanium dioxide, activity is higher in UV and visible radiation. Photocatalysts are expected to be widely used against many harmful pathogens.

The use of the excellent photocatalytic effect of TiO ₂ with the generation of a strong oxidant on the surface in the form of a hydroxyl radical is a technologically feasible technology, and its production on an industrial scale is relatively easy and inexpensive.

The simplest and at the same time very effective way is to paint walls and ceilings with paint containing a photocatalyst.

 But aren't such measures harmful? For man, the environment?

– In the case of traditional methods, e.g. disinfection with chlorine compounds, this is associated with the appearance of carcinogenic Cl ₂ . Changes in water quality regulations have led to greater emphasis on alternative disinfection mechanisms. The use of ozone is quite troublesome due to the need to have an inexpensive ozone generator and a very short "life" of ozone (short half-life), which does not permanently protect the environment.

Titanium dioxide TiO ₂ in building materials (walls, ceilings, floors, etc.) is naturally less harmful to the environment. Photoactive materials adsorb pollutants and microorganisms on their surface, and then inactivate or decompose into carbon dioxide and water under the influence of UV radiation and visible radiation available even in ordinary lighting bulbs. Photoactive materials do not release toxic by-products into the environment (like typical chemical preparations) and ensure effective and continuous disinfection of the environment.

How can we use these discoveries in our daily lives? If such surfaces, walls and ceilings, covered with photocatalytic paints work effectively in health care, will they work in residential spaces? Can they help reduce infections in apartments?

– Photocatalytic surfaces can be superhydrophilic, meaning water spreads over the surface, allowing dirt to be washed away, e.g. in commercial applications used to produce self-cleaning windows (e.g. San Gobain Bioclean™, Pilkington Active™ and Sunclean™) and such glass covers for tunnel lighting lamps. Of course, these are transparent coatings.

The photocatalyst can be used to coat walls, tables and other surfaces to reduce infections associated with infection through indirect contact. Wall tiles (tiles and grout) coated with TiO ₂ are also an effective self-cleaning and disinfecting material. Infection by influenza viruses spread by droplets (coughing, sneezing) can be limited indoors by adsorbing them on photoactive surfaces.

Therefore, covering walls and ceilings with paint containing a photocatalyst can effectively limit the spread of microorganisms, including pathogenic ones, as presented above in the short list of literature descriptions.

Aren't such photocatalytic products too complicated to use?

– Photocatalytic paints are easy to use. They do not require the use of special application technologies or special equipment. Coatings are made using traditional methods, using a brush, roller or spray. Since they are water-soluble, there is also no problem with odor, and the equipment can be washed with water.

The author of the text is PIGMENT, a manufacturer of photocatalytic paints with the trade name TITANIUM®. We invite you to check out our offer for Titanium IN , now at a new, lower price.