By Ben
Coxworth
April 07, 2022
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The filter has already successfully purified E.
coli-tainted water, and should be equally effective at neutralizing other
pathogens Photo credit: Depositphotos
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The flat-bodied prototype device was designed
at Switzerland's EPFL research institute, by a team led by Prof. László Forró.
Water enters via a tube in the top, flows through a multilayer composite
material sandwiched between two sheets of glass, and exits through a tube in
the bottom.
The composite material is made up of titanium
dioxide nanowires interwoven with carbon nanotubes. When the filter is exposed
to sunlight, the ultraviolet spectrum of that light causes the composite to
produce a group of molecules known as reactive oxygen species (which include
hydrogen peroxide, hydroxide and oxygen).
The small-scale prototype photocatalytic filter
L. Forro
These molecules are highly effective at killing
harmful bacteria and viruses – the filter has already been successfully tested
on water containing E. coli bacteria, with results indicating that it
should also have no problem eradicating other pathogens. In fact, it is
believed that the technology may also prove effective at eliminating
micro-pollutants such as pesticides and drug residues.
It should be noted that when activated by UV
light, titanium dioxide nanowires on their own are capable of killing microbes.
For that matter, even UV light alone can purify water, if the water
is left sitting in the sunlight in a transparent container.
However, Prof. Forró told us that his team's
filter is much more effective – this is due in part to the carbon nanotubes'
ability to absorb heat from the sunlight, accelerating the purification
process. The present small-scale model can treat 2 liters (0.5 gal) of water
per day, although that figure would rise considerably if the technology were to
be scaled up. Adding a small amount of gold nanoparticles to the composite may
further boost its performance.
"In
a close collaboration between chemists, physicists, and biologists, we have
developed a very efficient water purification device, which does not need any
energy source but sunlight," said Forró. "Our prototype can supply
clean drinking water even at remote places."
A paper on the research was recently published in the journal Nature.
Source: EPFL via AlphaGalileo