The chemistry at work

The Titanium AOP System works by a physical process. It exploits the effect of UV light upon a Titanium Dioxide surface in the presence of water. The resultant Hydroxyl (free) Radicals are highly reactive, attack and eradicate not only waterborne organisms but also any organic pollutants present. Therefore to understand the Titanium AOP system of treatment it is important to understand what a Hydroxyl Radical is and how we can create it.

What is a Hydroxyl Radical (OH)?

It is a very reactive, unstable and aggressive radical, oxidising any organisms and organic structure unselectively and indiscriminately.

The Advanced Oxidation Process uses a reaction created between UV light, Titanium Dioxide and water to generate the Hydroxyl Radical.

The Titanium AOP relies on the production and reactivity of Hydroxyl Radicals (OH) produced from water. The system uses a combination of photo-chemistry and photocatalytic reactions driven solely by electrical energy without the use of chemicals. The power needed for the formation of these free radicals is supplied as UV-light. This uses 20,000 times less energy than thermal disinfection. The high-energy UV photons pass through the reactor and drive three major processes:

• Photolysis Reaction
• Photo Oxidation
• Photocatalytic Reaction

PHOTOLYSIS REACTION
Hydroxyl Radical OH is produced when UV light with a wavelength of 185Nm reacts instantly with water converting H2O to OH.

First wave length 185 nm => Transforms H2O into OH radical. In the Titanium AOP process this reaction produces modest numbers of Hydroxyl Radicals.

PHOTO OXIDATION
A Photo Oxidation reaction occurs when the high intensity UV light meets the Titanium Dioxide surface. It will immediately oxidise any organism or organic matter at the surface.

PHOTOCATALYTIC REACTION

A photocatalytic reaction  occurs when UV light  with a wavelenghth of  254Nm reacts with Titanium Dioxide TiO2 to produce OH Hydroxyl Radical. The presence of the UV light promotes electrons at the surface of the Titanium Dioxide to a higher energy level creating an electron/hole (TiO2 e-h+) pair. Most promoted electrons will return to their lower energy level state by emitting light. Those that do react with water at the TiO2 / H2O interface produce Hydroxyl Radicals.  The species oxidise any organic matter present by removing a hydrogen atom.  If no organic matter exists the hydroxyl radical will recover hydrogen to reform into water. The Titanium AOP system does not affect pH, proving that all Hydrogen ions are converted back to water within the chamber.

Second wavelength 254 nm =>Transforms TiO2 into TiO2 e-h+ (electron hole)

OH radical oxidises organism to transform back into H2O

TiO2 e-h+ is a catalyst for production of OH radical near the surface of the tube

TiO2 e-h+ radical oxidises organism near the surface of the tube

By the action of the water flow passing through the reactor (an oxidation hot zone) the whole liquid volume is not only disinfected but in addition both organic and microbiological matter are decomposed. Due to their extreme reactivity Hydroxyl Radicals only exist for a matter of milliseconds before reverting back to water.  As a result all reactions only take place within the titanium reactor.

In the Titanium AOP process this reaction produces a mass proliferation of Hydroxyl Radicals.