These new membranes are structured at the nanoscale (the width of human hair is approximately 100,000 nanometers) to create molecular tunnels through which water flows more easily than contaminants. Unlike the current class of commercial reverse osmosis (RO) membranes, which simply filter water through a dense polymer film, the new membrane contains specially synthesized nanoparticles dispersed throughout the polymer — known as a nanocomposite material.
“The nanoparticles are designed to attract water and are highly porous, soaking up water like a sponge, while repelling dissolved salts and other impurities,” Eric Hoek from the University of California, Los Angeles said. “The water-loving nanoparticles embedded in our membrane also repel organics and bacteria, which tend to clog up conventional membranes over time.”
With these improvements, less energy is needed to pump water through the membranes. Because they repel particles that might ordinarily stick to the surface, the new membranes foul more slowly than conventional ones. The result is a water purification process that is just as effective as current methods but more energy efficient and potentially much less expensive. Initial tests suggest the new membranes have up to twice the productivity — or consume 50 percent less energy — reducing the total expense of desalinated water by as much as 25 percent.
A critical limitation of current RO membranes is that they are easily fouled — bacteria and other particles build up on the surface and clog it. This fouling results in higher energy demands on the pumping system and leads to costly cleanup and replacement of membranes.
COMPAMED.de; Source: University of California, Los Angeles