Then there is Harvey Reid [?] [a silverlister]
That impregnated saw dust with silver [nitrate?] and mixed it with clay to
fire, making activated carbon/silver ceramic pot water filters [in Africa?]
" Barefoot Native tech".....on a shoe without even a string from WalMart.
Now, to hook it up to a solar panel and pass a few microamps through it
all......
ode
At 07:11 PM 8/31/2010 -0500, you wrote:
Some extracts from the article are below.
- Steve N
<http://www.rdmag.com/News/2010/08/Materials-Nanotechnology-High-speed-filter-uses-electrified-nanostructures-to-purify-water-at-low-cost/>http://www.rdmag.com/News/2010/08/Materials-Nanotechnology-High-speed-filter-uses-electrified-nanostructures-to-purify-water-at-low-cost/
High-speed filter uses electrified nanostructures to purify water at low cost
By dipping plain cotton cloth in a high-tech broth full of silver
nanowires and carbon nanotubes, Stanford researchers have developed a new
high-speed, low-cost filter that could easily be implemented to purify
water in the developing world.
Instead of physically trapping bacteria as most existing filters do, the
new filter lets them flow on through with the water. But by the time the
pathogens have passed through, they have also passed on, because the
device kills them with an electrical field that runs through the highly
conductive "nano-coated" cotton.
Silver has long been known to have chemical properties that kill bacteria.
"In the days before pasteurization and refrigeration, people would
sometimes drop silver dollars into milk bottles to combat bacteria, or
even swallow it," Heilshorn said.
Cui's group knew from previous projects that carbon nanotubes were good
electrical conductors, so the researchers reasoned the two materials in
concert would be effective against bacteria. "This approach really takes
silver out of the folk remedy realm and into a high-tech setting, where it
is much more effective," Heilshorn said.
Using the commonplace keeps costs down
But the scientists also wanted to design the filters to be as inexpensive
as possible. The amount of silver used for the nanowires was so small the
cost was negligible, Cui said. Still, they needed a foundation material
that was "cheap, widely available and chemically and mechanically robust."
So they went with ordinary woven cotton fabric.
"We got it at Wal-mart," Cui said.
To turn their discount store cotton into a filter, they dipped it into a
solution of carbon nanotubes, let it dry, then dipped it into the silver
nanowire solution. They also tried mixing both nanomaterials together and
doing a single dunk, which also worked. They let the cotton soak for at
least a few minutes, sometimes up to 20, but that was all it took.
--
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