researchers from the Gauhati University, Assam, have developed a neem leaf powder (nlp) that acts as a dye remover and also helps get rid of heavy metals such as lead and chromium from solutions. "A small amount (1 gramme) of nlp could remove as much as 95 per cent of Congo Red dye and 1.2 g of nlp could remove 93 per cent of lead from aqueous solution,' says Krishna G Bhattacharyya, the lead researcher.

"The nlp contains fine particles of indefinite shape and size with a large number of steps, pores and kinks on the external surface, which could trap (adsorb) Congo Red molecules,' says Arunima Sharma, co-researcher. The findings of their studies were published in the Journal of Environment Management (Vol 71, No 3) and the Journal of Hazardous Materials (Vol 113, Nos 1-3). While Congo Red dye is a complex organic compound, which if ingested is converted to benzidine, a known human carcinogen, lead is toxic for brain cells and chromium for skin and lungs. These substances can be removed with the help of granulated activated carbon or powdered activated carbon, but their cost works out to be prohibitive and the disposal of the used carbon is often very difficult. To search out a cheaper disposal method, the researchers crushed, washed and dried mature neem leaves and then converted them into a powder, which was further washed and dried before being used as a dye remover.

nlp was then added to a dye solution in a conical flask, which was put in a mechanical shaker and continuously agitated at 27