Laboratories of various kinds use water. The
regular
water flowing out of the tap isn't up to standard due to
contaminants. Which type of contamination matters
varies
very much between types of science.
Often, labs will buy an expensive machine <link> which
uses many layers of filtration
to sterilize (UV light) and
filter (reverse osmosis) to produce water with a
resistance
of 18.2 M Ohms/cm. This is pretty clean water. It does
retain contamination, for example, it has micromolar
amounts of dissolved calcium, which is about 1000 fold
too
high for the sorts of experiments I occasionally attempt.
So
solving that problem involves boring steps with expensive
chemicals. Anyhow, the water machines have other
problems. The main one, is that no one ever wants to
buy
the replacement filters. We can do better.
So, I propose a different strategy. 1st step, regular cheap
0.22uM filter. Just to keep the larger chunks out. This
feeds into step 2, a boiling vessel. Here around 50% of
the water
is
vaporized, the rest drains away taking concentrated
minerals etc. The boiling is done by one of those nifty
high
temperature Peltier elements at almost exactly 100 C,
the
vapor travels up and over a gas bridge to condense on the
cold side of the same element. Here too, there should be
a
portion of water outflow, to ensure a constant washing
but... the temperature is JUST a hair under 0 C. The rate
of water outflow should be passively controlled by gas
pressure from the next step, a nice safety feedback
measure.
Step 3 the ice portion is scooped out by a
wheely
thing and delivered to a warmed electrolysis
chamber, or electrolytic hydrolysis if you will. Water is
split at two electrodes into two separated streams of
Gas,
H2 and O2. The pressure of either/both of these gasses
feeds back to the water step to prevent any untoward
build up of dangerous stuff.
The gas streams can then pass up and over another
bridging structure, through gas-selective membranes if
you're feeling fancy.
Step 4, the gas flows down past a platinum catalyst,
or
a fuel cell if you're feeling efficient, but that's not from
grant money, so screw it. Here, the H2 and O2
recombine
to form nice clean water.
Now, contamination is possible, but the contaminants
would have to have similar boiling point to water,
similar
freezing point to water, similar gaseous electrolysis
products to water and similar platinum catalysed
reaction
products to water. Walks/quacks like a duck... Should be
cheaper than the alternative.