Using sunlight-activated photo-catalysts to disinfect water

A round table discussion with Dr Vasant Kumar from the Materials Department on a new method to disinfect water at low cost with no power required.  This talk is part of the Winton Discussions series.

Abstract:

Sunlight can degrade pollutants in water and atmosphere with a suitable photo-catalyst. A number of current technologies are on offer, with the most common catalyst being titanium dioxide particles or coatings. These have the advantage of working with sunlight, with no need for an external power source, so the pollutant removal can take place off-grid and is cheap to operate. However, the currently-available catalysts only exploit the ultraviolet part of the spectrum, resulting in a slow degradation process which is slowed further by cloudy weather conditions.

Dr Kumar and co-workers from the Department of Materials Science & Metallurgy have developed a new sunlight-activated catalyst which is active in the visible range of the spectrum. The reaction speed is 1 – 2 orders of magnitude as fast as that of catalysts like titanium dioxide, since more of the sunlight's energy is used. It can also work in low light conditions including cloudy weather and indoors (using ambient sunlight and/or artificial light).

This new patented photo-catalyst potentially has a wide range of uses for water purification and atmospheric hazard / pollutant removal. Some examples include the market for textile dyes, where 0.7 million tons of dyes are produced every year worldwide, with 10% being released in the effluents; purification of drinking water without the need for a power source or replacement filters; systems for hazard destruction in crowded centres; and a low cost, zero power solution for the purification of air inside buildings.