Cleaning up pollutants with sunlight

A cheap, harmless chemical and sunlight could provide an environmentally friendly way of destroying micro-pollutants in the environment.

UK researchers are developing a new type of reactor to destroy persistent contaminants such as pesticides and pharmaceutical residues.

The technology, which breaks down the polluting molecules into carbon dioxide and water, could provide a breakthrough for a sustainable way of cleaning up fresh water supplies and industrial wastewater.

The work is being led by Dr Gianluca Li Puma at the University of Nottingham. The project is funded by the Swindon based Engineering and Physical Sciences Research Council.

The Nottingham team is investigating a novel type of reactor, the ‘fountain photo-catalytic reactor’, to treat contaminated water, using titanium dioxide. The idea is to pump the contaminated water through a specially designed nozzle. Titanium dioxide is then added to the water. The nozzle produces an umbrella-shaped fountain of water, with the sunlight – or artificial ultraviolet light – falling on the ‘canopy’ of the umbrella. This allows the photo-catalyst to absorb the solar radiation efficiently, resulting in a more effective destruction of the pollutants.

“Once the pollutants have been removed the water can be passed to a settling tank where the titanium dioxide can be recovered and re-used for the same process,” says Dr Li Puma.

The team has successfully demonstrated the feasibility of the concept using a 400 litre pilot plant and ultraviolet lamps to simulate sunlight.

“We see this as being a potentially sustainable technology which could have particular use in countries with plenty of sunshine, such as southern Europe, Central and South America, Africa and the Asia/Pacific region,” says Dr Li Puma. “In the UK the present technology can use low-cost, low-power sun-tanning lamps.”