Cotton produces effective purifier
Nanotech zapping makes leap into biofuels market in a safe but productive into an industry due to gain significant financial support
Removing
bacteria and other harmful microorganisms from water is an exceptionally
important process; letting too many of these little monsters into your gut can
be exceedingly dangerous. Needless to
say, any measure that can help reduce their influence on an industrial level,
such as in major biofouling events, is also to be warmly welcomed. Thanks to the ingenious efforts of a team of
researchers at Stanford University, such a measure is now in our midst. Their new water-purifying filter coats
ordinary cotton fibres with carbon nanotubes and silver nanowires. In addition, it’s 800,000 times faster than
existing filters.
Instead
of simply trapping pathogens in the fibres, as conventional cotton filters do,
the new filter works by zapping them: the nano-coating is highly electrically
conductive. Lab tests were
extraordinarily promising. When multiple
layers of the nano-coated mesh were used, 98 percent of Escherichia coli bugs
met an untimely end within seconds when a mere 20 volts of electricity was
applied across the filter. In practise,
even small voltages can be safely used, like that provided by a 12-volt car
battery or a single solar panel.
Cotton
cloth is dipped first into a soup of nanotubes, each of them only a few
billionths of a metre in length and an incredible single billionth of a metre
in diameter. After it’s dried, the cloth
is then plunged into a broth of silver nanowires, ranging in diameter from 40
to 100 billionths of a metre and reaching just 10 millionths of a metre in
length. The resulting mesh is then
electrified.
The
development is ideally suited for water treatment in developing countries and
remote areas more generally, where there is little or no access to chemical
treatments such as chlorine. Associate
professor of materials science and engineering at Stanford, Yi Cui, believes
that the new filter will help eradicate water-borne illnesses such as cholera,
typhoid and hepatitis in the developing world; it can be deployed in water purifying
systems located not only in cities but also in small villages.
Because
the new filter relies on zapping the pathogens rather than trapping them, it
instantly overcomes the problem of pore size in conventional filters. The latter have to trap bacteria, which means
that pores must be small enough to do so – and this inevitablty slows down the
water flow rate. The new filter has much
larger pores, allowing water to surge through much, much faster and preventing
clogged.
To be
precise, it’s the highly conductive carbon nanotubes that do the electrical
zapping; the silver used to make the nanowires has long been known to kill
bacteria biochemically. This is the
chief antidote to biofouling, which is usually caused by pathogens forming a
film on the filter. Any lingering bugs
on this filter, if they haven’t met a sticky end with the small electrical
charge, will be destroyed by the silver.
Moreover, because the quantity of silver used in the nano-engineered
cotton is so small, the costs of production will be exceptionally low. Not only that, but the filter does way with
the costly and energy-greedy electrical pumps that are used to force water
through “bug trapping” conventional filters.
Because of those large pores, gravity is all it takes to move the water
through the nano-filter.