Two membranes are better than one at purifying water

Globally, polluted water kills 14,000 people every day.  In India, over 350,000 children die of diarrhoea from dirty drinking water every year.  In China, 90% of cities suffer from some type of water pollution.  In the US, a recent study found contaminants in 45% of the country’s stream miles and 47% of lake acres.  Despite the UN declaring access to clean drinking water a basic human right in July 2010, 884 million people worldwide still go without.  However, a new breed of membrane filter could help to turn the filthy tide.

Until now, removing organic toxins meant forcing dirty water through filters at inefficiently high pressures or cleaning it with expensive chemicals.  But researchers from the universities of Kentucky and Miami have combined the best of both these methods, creating a stack of membranes that operates at low pressure and does away with the need for chemicals.

The scientists sandwiched iron nanoparticles between polymer sheets whose nano-scale pore size can be controlled by changing the amount of light, pH or concentration of the solution.  The team’s results, published in this week’s Proceedings of the National Academy of Sciences show that their membranes effectively remove trichlorophenols – significant contaminants in US waterways – from both test solutions and real groundwater samples.

The team believes that this is just the beginning and that membranes like theirs will soon be capable of killing viruses and purifying water infected with all types of toxins.


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