researchers in Maharashtra have found powdered leaves of common trees such as neem, pipal and khair can remove fluoride from drinking water. Ingested daily, even as little as 6 milligramme of fluoride can cause fluorosis, which is endemic in 17 states in the country.
Scientists from Yavatmal-based Jawaharlal Darda Institute of Engineering and Technology (jdiet) and Amaravati University first treated the leaf powder with nitric acid and then with sodium hydroxide. The scientists then dried it in the sun. When added to water containing 15 mg of fluoride per litre, the powder adsorbed (captured) almost all the contaminant in about three hours, according to a paper published in the September-October issue of the Journal of Indian Institute of Science (Vol 84, No 5) .
Led by A V Jamode of the Department of Chemical Engineering at jdiet, the researchers also found the powder's efficacy varied from 50 to 90 per cent depending on how finely it was ground. With particles of 0.6 millimetre (mm) diameter, the powder (40 grammes per litre) could remove about 90 per cent of fluoride at a concentration of 10 mg per litre, whereas this ability fell to nearly 50 per cent when the diameter of particles was 1.4 mm. This is because for the same quantity of powder, small particles provide greater surface area than the bigger ones.
Some other plant products have also been known to remove fluoride from water. These include sunflower plant dry powder, neem bark powder and activated cotton jute carbon. But these either had low efficiency or were unsuitable for mass scale applications. The scientists claim the powder they have developed would be especially suitable for treating fluoride contamination in rural areas. But A K Susheela of Delhi-based Fluorosis Research and Rural Development Foundation says such techniques have to be first proven in the field on a large scale.
"In most experiments what happens is researchers will use distilled water in which some flouride salts are dissolved. The potential adsorbants are then tried out.' But the water people have access to usually has a large number of dissolved salts. "Such an environment is completely different from the one in the lab,' she cautions.