About one in nine people worldwide
lack access to clean water; over 3.4 million deaths each year from water,
sanitation and hygiene related causes, according to water.org. In fact, goal 7,
target 10 of the MDGs aims at halving, by 2015, the proportion of people without
sustainable access to safe drinking water and basic sanitation. One of the overarching
engineering challenges today is developing some technology that will solve the world’s
water woes – in other words, turn polluted water to potable water.
Actually, the
problem is not that of insufficient water (71% of our planet's surface is water,
97% of it in seas and oceans) but of clean, potable water. Much of the available water is either bacteria ridden
or just too salty, either way, unsafe for consumption. Quite a number of solutions are already mainstream, all with the intent of solving
the world’s water problems (I wouldn’t suppose they have done so amazing given
those horrifying statistics staring us dead in the face) perhaps most notable
of those are the desalination (by reverse osmosis) and water reclamation (recycled water) processes. Some regions
of the world with no or limited surface or groundwater have seen desalination and waste water treatment become a major
source of potable water (Saudi Arabia is a
shining example), however unconventional that may be. The problem here
is that these technologies are very energy intensive (in Almeria province, Southeastern
Spain, one-third of all the power produced in that region go into a desalination
plant) and expensive (typically costing hundreds of millions of dollars),
making it beyond the reach of most of the developing world, who by all
indications need it most. So can we actually have an efficient, affordable
water purification technology that can make clean water available to more
people than ever before? You're set to find out.
It seems the ultimate answer lies
somewhere we can’t even see, the microscopic world…or should I say, nanoscopic world The key ingredient here is something called graphene (a form of carbon only one-atom thick!). MIT
associate professor, Jeffrey C. Grossman, and his graduate students David
Cohen-Tanugi and Shreya Dave are developing a filtration material made of a
sheet of nanoporous graphene. The holes in the graphene are small enough to
block salt ions, but large enough to allow water molecules to pass through. In fact, researches on graphene have been on-going for quite a while but only now being
looked at for water applications. Unlike the energy intensive reverse osmosis (RO)
technique of desalination (happens to be the most efficient desalination process available today)
which rely on semipermeable membranes for separating salt from water and
require large pressure to force the salt water through them; nanoporous graphene are
much thinner, more porous, stronger and provide a well-defined channel that can filter salt water faster than
the rather slow RO process, even while requiring lower pressure.
From simulations, nanoporous
graphene have been shown to outperform RO membranes. The few challenges however are, achieving
a narrow pore distribution size, and mechanical stability under applied
pressure the scientists say; although rapid experimental progress is being made with regard to tackling those issues. So far, results are so promising that it won’t be long before
graphene membranes are put to the test in desalination and decontamination, and whoosh…we’re one step closer to
realizing one MDG ahead of 2015. Gotta love science!
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| Nanoporous graphene in desalination |
very expository
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