A water desalination system using carbon nanotube-based membranes could significantly reduce the cost of purifying water from the ocean. The technology could potentially provide a solution to water shortages both in the United States, where populations are expected to soar in areas with few freshwater sources, and worldwide, where a lack of clean water is a major cause of disease.
The new membranes, developed by researchers at Lawrence Livermore National Laboratory (LLNL), could reduce the cost of desalination by 75 percent, compared to reverse osmosis methods used today, the researchers say. The membranes, which sort molecules by size and with electrostatic forces, could also separate various gases, perhaps leading to economical ways to capture carbon dioxide emitted from power plants, to prevent it from entering the atmosphere.
The carbon nanotubes used by the researchers are sheets of carbon atoms rolled so tightly that only seven water molecules can fit across their diameter. Their small size makes them good candidates for separating molecules. And, despite their diminutive dimensions, these nanopores allow water to flow at the same rate as pores considerably larger, reducing the amount of pressure needed to force water through, and potentially saving energy and costs compared to reverse osmosis using conventional membranes.