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Posted: Jun 22, 2011

Nanocoated 'super sand' for better purification of drinking water

(Nanowerk News) Scientists have developed a way to transform ordinary sand — a mainstay filter material used to purify drinking water throughout the world — into a "super sand" with five times the filtering capacity of regular sand. The new material could be a low-cost boon for developing countries, where more than a billion people lack clean drinking water, according to the report in the ACS journal Applied Materials & Interfaces ("Engineered Graphite Oxide Materials for Application in Water Purification").
nanocoated sand
Retaining the inherent hydrophilic character of GO (graphite-oxide) nanosheets, sp2 domains on GO are covalently modified with thiol groups by diazonium chemistry. The surface modified GO adsorbs 6-fold higher concentration of aqueous mercuric ions than the unmodified GO. "Core–shell" adsorbent granules, readily useable in filtration columns, are synthesized by assembling aqueous GO over sand granules. The nanostructured GO-coated sand retains at least 5-fold higher concentration of heavy metal and organic dye than pure sand. (© ACS)
Mainak Majumder and colleagues note that sand has been used to purify water for more than 6,000 years, and sand or gravel water filtration is endorsed by the World Health Organization. Their studies of a nanomaterial called graphite oxide (GO) suggest that it could be used to improve sand filtration in a cost-effective way, they write.
The researchers used a simple method to coat sand grains with graphite oxide, creating a super sand that successfully removed mercury and a dye molecule from water. In the mercury test, ordinary sand was saturated within 10 minutes of filtration, while the super sand absorbed the heavy metal for more than 50 minutes, the scientists discovered. Its filtration "performance is comparable to some commercially available activated carbon," the scientists said. "We are currently investigating strategies that will enable us to assemble functionalized GO particles on the sand grains to further enhance contaminant removal efficiencies," they write.
Source: American Chemical Society
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