Is the Ti02 catalyst carcinogenic ?
The carcinogenicity of a chemical element is directly related to its size and therefore its propensity to infiltrate lung tissue at depth, for instance.
The specific feature of photocatalysis is that it uses the Ti02 device in its microscopic as opposed to its nanoscopic format. The size is therefore several hundred nanometres. What's more, it seems that if particles work lose, they immediately form an aggregate a few microns in size, which is too large to allow them to infiltrate the pulmonary alveoli at depth.
This system seems to generate ions that are toxic for the airways (active oxygen O2- and hydroxyl radicals)?
Photocatalysis, as used by Biowind, does not produce ions but free radicals. In fact, O2°- is closer to a radical than an ion. The specific feature of free radicals is that they are several million times more reactive than ions. This is why, right from the outset, when they first appear on the surface of the catalyst, they react on coming into contact with pollutants. Furthermore, their average life-span is only a few pico seconds. They therefore only cover a few nanometres on the surface of the catalyst. Hence they cannot penetrate ambient air. This is why photocatalysis is described as a "surface process".
How does photocatalysis affect viruses, bacteria, fungi and, above all, spores ?
The photocatalysis process attacks the cell wall of the microorganisms. Photocatalysis is a surface reaction. The microorganisms are thus "torn open" in some way, which ultimately disrupts their respiratory activity and leads to their death (we refer to "death" since they are living organisms, apart from viruses). The tests carried out at the CNRS on BIOWIND technology have shown that this activity was due to the combined action of the catalyst used and the photons that activate it. UV-A rays alone do not affect micro-organisms. Some tests carried out by the CNRS (from 2007 onwards) have shown greater elimination (3 log) of bacteria, spores and viruses. The tests were carried out under extreme conditions: at concentrations of 1.5 * 10^5 species / litre of air as shown in the CNRS test reports. These are exceptionally high concentrations that are not found in ambient air.
On which pollutants is photocatalysis devoid of effect ?
Chlorofluorocarbons (CFCs), nitrogenous and sulfur compounds are difficult to be destroyed by photocatalysis.
Which pollutants are destroyed by photocatalysis ?
Group A - 7 "high priority" substances: formaldehyde, benzene, acetaldehyde, di-ethylhexyl-phthalate (DEHP) and dichloros; Group B - 12 "high priority" substances: dog allergens, mites, toluene, trichlorethylene, lead, tetrachloroethylene, dieldrin, cat allergens, aldrin and short-chain chlorinated paraffins. Group C - 51 "priority" substances including biocides, volatile organic compounds, glycol ethers, endotoxins, phthalates, organotins. Group D -22 "non-priority" substances including 1,1,1-trichloroethane, biocides, phthalates (DMP), alkyl phenols and organotins.
What is the photocatalytic efficacy depending on the type of pollutants ?
The oxidation rate (efficacy of photocatalysis) of the various chemical species follows in general this order: alcohols & glycol ethers > aldehydes, ketones and terpene hydrocarbons > aromatic and alkane hydrocarbons > aliphatic halogenated hydrocarbons.
What is the maximum operating temperature? Can photocatalysis be incorporated in a process or used in an area where the temperature can reach 100°C at times?
Photocatalysis can function at temperatures ranging from 0 to 100°C, preferably between 20 and 80°C. Its optimum temperature is room temperature. Recently, we carried out tests with boat exhaust emissions (NOx, hydrocarbons, etc.); the outlet temperature was 120°C (temperature on leaving the exhaust pipe: 350°C). We recorded a decrease of 5 to 50% depending on the type of pollutants.
Can photocatalysis be incorporated in a process or used in an area where the temperature can reach 100°C at times ?
Yes. In this case, the BIOWIND system is installed using the ventilation function of the existing air conditioning unit. Check that the existing ventilation system can accept (minimal) pressure drop from the BIOWIND system.