High-speed, low-cost water purification

Researcher Yi Cui, associate professor of materials science and engineering at Stanford University, hopes a nanotube- and silver-enhanced piece of plain cotton fabric will bring clean drinking water to poor and remote locations in developing countries. Cui and his team created a water filter from cotton dipped in carbon nanotubes and silver nanowires which, when attached to a couple of 12-volt car batteries, can remove 98 percent of E. coli bacteria more than 80,000 times faster than existing water filters. “This really provides a new water treatment method to kill pathogens,” says Cui. “It can easily be used in remote areas where people don’t have access to chemical treatments such as chlorine.”

Most water filters work by trapping bacteria in small pore spaces. These small pores reduce water flow and, once full of bacteria, clog the filter. Water flows rapidly through the Cui filter, where bacteria die after they encounter electrical current carried and distributed by the carbon nanotubes. Any pathogens that linger are destroyed by the antimicrobial properties of the silver nanowires. Research continues on permutations of the high-speed filter that can remove other pathogens (such as cholera, typhoid and hepatitis) and act in series to achieve 100 percent removal of bacteria.