In 1972, PhD student Akira Fujishima of Tokyo University and his supervisor Professor Kenishi Honda were searching for new technologies for hydrogen production. The result of their work was an article in the prestigious journal Nature. In the article, the process of decomposition of water on the surface of titanium dioxide (TiO2) crystals under the influence of sunlight, was described for the first time.
This process was named photocatalysis. In 1985, in Japan again, just enrolled in the postgraduate course of Tokyo University, Takehiro Matsunaga (Takehiro Matsunaga) told the world about the bactericidal properties of TiO2. Since then, hundreds of scientific works have been written on the topic of photocatalysis.
So what photocatalysis is? Photocatalysis is a process of acceleration of chemical reaction, due to the combined action of the catalyst and light. Within 6 hours, the tobacco resins applied to the photocatalyst element under the action of UV radiation completely decompose into water and carbon dioxide.
Removal of tobacco resins from the surface of the photocatalytic element under the influence of UV radiation
Let us review the photocatalysis reaction in detail:
TiO2 is a semiconductor. In such compounds, electrons can be in two states: free and bound. The usual state of the electron is bound, that is, it is connected with the ion of the crystal lattice of the substance, forming a strong chemical bond.
In order to "tear off" an electron out of the crystal lattice, it is necessary to apply at least 3.2 electron-volts (eV) of energy (for comparison, the kinetic energy of a flying mosquito is about a trillion eV). To our joy, it is this amount of energy that carries a quantum of light with a wavelength of less than 390 nM. Therefore, a quantum of light "knocked out" an electron from a lattice, forming an electronic vacancy, and easier ‑ a "hole".
Electron and hole actively move inside the TiO2 particle. Because of this movement, they either recombine (meet each other, "marry" and return to the bound state), or break out onto the surface and immediately grab it.
Both the "hole" and the electron are incredibly chemically active. The entire surface of the catalyst is the most powerful oxidation field. Touching the surface of the catalyst oxygen, giving a free electron as a gift, gives rise to the oxidative radical O-, which is capable of destroying (oxidizing) any organic compound. "Hole", in turn, itself reacts with the first organic compound it has met on the surface. "Hole" tears out the missing electron from the structure of the connection, thereby breaking the compounds themselves into water and carbon dioxide.
Each time the "spended" pairs of electron/hole being replaced by a new and new pairs, like bubbles in a glass of champagne, on the surface of the catalyst. The oxidation process will continue until the light is applied to the catalyst.
The photocatalytic filter mineralizes organic molecular impurities, mainly down to carbon dioxide and water
Our technological achievements:
Catalyst. The largest photocatalytic activity is TiO2 with a crystalline modification of anatase containing a minimal amount of impurities. We use in our devices just such a catalyst in the form of ultrafine powder of our own production. The particle size is about 40 nm. It is in this state that the catalyst is highly active and has a maximum reaction surface.
Carrier (a structural element on the surface of which TiO2 is applied). Requirements for media material are very severe: it can’t be made of organic materials, because under the influence of ultraviolet any organic substance decomposes, it must pass ultraviolet, and therefore it must be transparent, and finally, it must have a large surface for contacting the catalyst and air with small dimensions. We know how to make such carriers, getting a plate or a tube of sintered quartz balls with a diameter of 1 mm according to our own patented technology.
Quartz balls 1 mm diameter
TIVEIL devices principles of operation
Pre-filter - removes coarse dust from cleaned air.
Fan - ensures the flow of cleaned air through the device.
Electrostatic filter, - retains the smallest aerosol particles, bacteria, viruses and spores of mold.
Photocatalytic filter - Mineralizes organic molecular impurities, mainly to carbon dioxide and water. It consists of UV lamps operating in the "soft" radiation range (320-405 nm) and photocatalytic elements on an inorganic basis.
Coal-catalytic filter - prevents the breakthrough of harmful substances due to their adsorption on the surface of the carbon adsorbent. The technology of joint operation of adsorption and photocatalytic filters allows to make the adsorbent regenerating with increasing its service life up to 10 times.
Carbon monoxide purification unit - contains a Pt/Pd catalyst on a nanocrystalline carrier. In addition to carbon monoxide, it removes low-molecular organic compounds from the air (Option).
Power supply and signaling - includes a sensor system for automatic control (only for VR400A), which sets the operating mode of the air cleaner depending on the level of concentration of molecular organic contaminants in the air being purified.