Tuesday, April 24, 2007

Nanotechnology pesticide filter debuts in India

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Posted: April 20, 2007
Nanotechnology pesticide filter debuts in India
(Nanowerk News) A domestic water filter that uses metal nanoparticles to
remove dissolved pesticide residues is about to enter the Indian market. Its
developers at the Indian Institute of Technology (IIT) in Chennai (formerly
Madras) believe it is the first product of its kind in the world to be
Mumbai-based Eureka Forbes Limited, a company that sells water purification
systems, is collaborating with IIT and has tested the device in the field
for over six months. Jayachandra Reddy, a technical consultant to the
company, expects the first 1000 units to be sold door-to-door from late May.

The pesticide-zapping filter (Image: Thalappil Pradeep)
'Our pesticide filter is an offshoot of basic research on the chemistry of
nanoparticles,' Thalappil Pradeep who led the team at IIT Chennai told
Chemistry World. He and his student Sreekumaran Nair discovered in 2003 that
halocarbons such as carbon tetrachloride (CCl4) completely break down into
metal halides and amorphous carbon upon reaction with gold and silver
nanoparticles ("Halocarbon mineralization and catalytic destruction by metal
nanoparticles"; pdf download 136 KB).
Pradeep said this prompted them to extend their study to include
organochlorine and organophosphorous pesticides, whose presence in water is
posing a health risk in rural India. In research funded by the Department of
Science and Technology in New Delhi, his team found ("Detection and
extraction of endosulfan by metal nanoparticles" and "Extraction of
Chlorpyrifos and Malathion from Water by Metal Nanoparticles" (in: J.
Nanosci. Nanotechnol. 7, 1871–1877 (2007) – not yet published)) that gold
and silver nanoparticles loaded on alumina were indeed able to completely
remove endosulfan, malathion and chlorpyrifos - three pesticides often found
at elevated levels in Indian water supplies.
Use and recycle
The mechanism of removal is 'adsorption followed by catalytic destruction',
Pradeep explained. 'The chemistry occurs in a wide concentration range of
environmental significance.' He added that tests proved silver particles
from the filter are not released into the water. The IIT study found that
gold particles perform better in the case of endosulfan. However, for cost
reasons, the commercialised filters use only silver particles, which range
in size from 60 to 80 nanometres at a concentration (on their alumina
support) of 33 parts per million.
'Based on consumption patterns of a typical Indian household, the filter is
designed to have enough nanomaterials to provide 6000 litres of
pesticide-free water for one year,' Pradeep said. 'After that, the company
will recycle the filters to recover the silver.'
Use of nanoparticles for environmental remediation is an emerging area of
research worldwide. Nanoscale iron powders had been shown to degrade other
pesticides, including DDT and lindane ("Nanoporous zero-valent iron"), 'and
there are reports about the use of nanomaterials for removing arsenic, heavy
metals and fluorides,' said Pradeep. 'But ours is the first product to hit
the market,' he said.
World first
Murali Sastry, chief scientist of TATA Chemicals Innovation Centre in Pune -
India's first nanotechnology research centre in the private sector - agrees.
'What Pradeep has done is definitely novel,' Sastry told Chemistry World. 'I
am not aware of any similar product in the market.'
Eureka already markets a water purifier that combines a sedimentation
chamber with activated carbon filters and UV irradiation, and costs around
Rs8500 (approx. $200). Reddy estimated that adding the x-centimetre-long
nanosilver cartridge (see image) to remove pesticides will increase the
price by 15 per cent, but silver recycling (in an environmentally-friendly
manner, stressed Pradeep) should help to reduce that cost.
Vijayamohanan Pillai, a nanomaterials expert at the National Chemical
Laboratory in Pune, pointed out that it is very rare for an Indian company
to exploit a home-grown nanotechnology. 'Most big companies in India look
abroad for collaboration,' he said. One problem is that scaling up
nanoparticle production is difficult. But Pradeep said his team had taken
three years to attack this problem, and 'Eureka Forbes can now make four
tonnes of silver nanoparticles a month.'
Source: Chemistry World (Killugudi Jayaraman)