PHOTOSPHERES® are hollow glass microspheres coated with photocatalytic titanium dioxide (TiO2).
In the presence of light in the near UV region, titanium dioxide generates reactive oxygen species and hydroxyl radicals capable of breaking down many organic and inorganic pollutants in wastewater, as well as destroying micro-organisms.
However, the TiO2 nanopowders historically used for this purpose are difficult, if not impossible, to recover from treated wastewater by conventional, high throughput filtration techniques.
By covalently bonding titanium dioxide on to the surface of hollow glass microspheres the resultant PHOTOSPHERES can be recovered through simple flotation and, if necessary, by filtration. They are comparable in performance to traditional TiO2 nanopowders. They are also reusable and the coating is continuous, smooth and robust and does not shed into the treated water
With a mean particle diameter of 45 microns, they represent the optimised handling and activity solution between the high surface areas offered by TiO2 nanoparticles, and the low surface areas of TiO2-coated panels and piping.
PHOTOSPHERES can be used in enclosed, artifically illuminated reactor formats using UV light sources. Their buoyancy also enables application in open water systems, such as tanks, ponds and lakes, where solar UV wavelengths stimulate the photocatalytic activity.
They show excellent photocatalytic activity against a range of water industry relevant organic pollutants and have also been demonstrated to be effective in reducing gaseous pollutants. (more info)
The titanium dioxide coating on PHOTOSPHERES is continuous, smooth and robust and does not shed into the treated water.
HIGH PHOTOCATALYTIC ACTIVITY
The graph below highlights the effectiveness of PHOTOSPHERES against a standard test substrate, Methylene Blue.
They have also shown high photocatalytic activity against humic acids, NOx gases and other substrates.
EASE OF COLLECTION
This model shows the simplicity with which PHOTOSPHERES can be used, collected and re-used.
Stage 1 – PHOTOSPHERES are added into polluted water.
Stage 2 – Agitation is achieved by air bubbling and UV provided by sunlight.
Stage 3 – Allowing the liquid to settle brings the PHOTOSPHERES to the surface.
Stage 4 – The clean water is drained leaving the PHOTOSPHERES ready to be reused.
Their ability to be used multiple times means that they are a more environmentally efficient product. Testing has shown that across forty trials, the same PHOTOSPHERES yielded near identical levels of high photocatalytic activity.