He was looking for ways to get the concentration of silver up enough in
the sawdust so that when fired with the clay into a porous charcoal/ clay
matrix, the charcoal would have enough silver surface to sterilize drinking
water as fast as it seeped though the ceramic charcoal matrix.
Apparently the only thing he came up with that was strong enough to leave
that much silver behind was silver nitrate and he wasn't very careful with
it and turned blue.
Potters use silver acetate in silver glazes.
ode
At 11:15 AM 9/1/2010 -0400, you wrote:
I was thinking that he ran salty water through the filter to convert the
silver nitrate to silver chloride, which is barely soluble so it would get
"stuck" in the matrix. I may be wrong though.
I remember we went back and forth here on several possible methods and
protocols before he settled on his final solution.
Marshall
Ode Coyote wrote:
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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