Activated carbon removes pesticide

activated carbon is commonly used in water purifiers. But even wasted activated carbon (wac) is useful -- it could remove atrazine, a pesticide, from domestic wastewater, claims a group of researchers from the Indian Institutes of Technology in Guwahati and Chennai.

"Wastewater favoured the growth of atrazine degrading bacteria on the surface of wac, enhancing its atrazine removal efficiency," says Ligy Philip, lead author of the study, which has been published in Journal of Environmental Science and Health Part B (Vol 40, No 3) .

wac removed atrazine, which is toxic to fish and frogs, even in the presence of other pollutants present in wastewater, claims co-author Pranab Kumar Ghosh. "The wac can be reused as adsorbent twice before its final disposal," he adds.

The team studied wac's atrazine removal efficiency in both distilled water and wastewater. The scientists took two fractions -- one only treated with distilled water and the other with acid -- of powdered wac (grain size 0.3-0.5 millimetre). With 100 millilitre of distilled water, 2 gramme/litre(l) of each fraction of wac and 5 milligramme/l of atrazine were shaken mechanically at 35 c.

"After 2 hours, wac treated with distilled water removed 88.8 per cent of atrazine while the acid-treated one removed 88.9 per cent of the toxic chemical," says Ghosh. "In a 200 hour-long study with wastewater, atrazine removal was enhanced between 110-125 hours due to the combined effect of bugs' activity and adsorption by wac, " he added.