A potentially harmful herbicide can be removed from water with improved efficiency using a method developed by US scientists.

James Economy at the University of Illinois, Urbana-Champaign, US, and colleagues have prepared a chemically activated fibre that acts as a filter to remove atrazine from water.

Atrazine, one of the most widely used herbicides in the US, is found in drinking water across the country. While its effects on humans have not been established, Economy says it is a potential carcinogen and may disrupt the production of normal hormones. The US Environmental Protection Agency has set a maximum contaminant level of only 3 parts per billion for drinking water.

According to Economy, the removal of atrazine from water is essential, not only in the US but also in China. 'It is critical to remove this toxic material from surface waters which arise from run-off from farms,' he explained.

Currently the best water treatment method uses activated carbons - porous materials with exceptionally high surface areas - that adsorb atrazine. However, it is known that the pore size of the activated carbon can have a strong effect on the ability of the activated carbon to adsorb atrazine, and that organic matter can block its pores.

Economy developed a fibrous form of activated carbon. It is prepared by coating a glass fibre with a polymer resin along with a catalyst to 'activate' it. The fibrous filter is then assembled into a cartridge for use. He found that this system is more efficient at removing atrazine from water down to the recommended 3 ppb level than an equal amount of commercially available granular activated carbons.

'The next challenge,' said Economy, 'is to design scaled-up systems which can be used to clean up the atrazine from water processing facilities from which drinking water is derived.'

Caroline Moore