Neem cleansing

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 c . The study found increasing the amount of nlp from 0.2 g to 1.0 g in the solution enhanced dye removal from 35 per cent to 49.9 per cent for an agitation time of just one hour. For lead, an increase in nlp from 0.2 g to 1.2 g for an agitation time of 20 minutes increased adsorption from 16.1 to 67.7 per cent. In case of chromium, an increase in nlp from 1.6 g to 14 g for a constant agitation time of 3 hours increased adsorption from 89.1 to 100 per cent. "Increase in nlp amount makes a large number of adsorption sites available leading to an increase in metal ion uptake," claims Bhattacharyya in a paper published in a recent issue of Adsorption (Vol 10, No 4).

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