Why Does Membrane Permeability Matter To Mewater Water Every

Why Does Membrane Permeability Matter To Mewater Water Everywhere Why Does Membrane Permeability Matter to Mewater Water Everywhere Why Does Membrane Permeability Matter to Me? “ Water, water, everywhere, Nor any drop to drink .†Samuel Taylor Coleridge, The Rime of the Ancient Mariner, 1834. With 71% of the Earth’s surface covered by water (Links to an external site.) , how then is the world facing a water crisis? Yes, water. The molecule of life. In crisis. According to a 2019 World Resources Institute report, 17 countries, 25% of the world’s population, face “extremely high†water stress (when water demand exceeds water availability), drawing down 80% of their available supply per year. Another 44 countries, 1/3 of the population, face “high†levels of water stress, withdrawing more than 40% of their supply annually. Population growth, industrialization and climate change continue to intensify the demand. To help ensure water security, research is focusing on biologically-inspired nanotechnologies that mimic cell membranes , and a process vital in all cellular systems: osmosis . Just under 3% of the world’s water supply is fresh- the kind needed for drinking, irrigation and municipal use. The remaining 97% is saltwater. However, large-scale systems for desalinating ocean water, turning saltwater into drinkable freshwater, have been operational for decades. As of 2018, almost 16,000 desalination plants are operating in 177 countries. Many use membrane-based, reverse-osmosis (RO) technologies. Under normal osmotic conditions, water flows through a semipermeable membrane from a hypotonic solution (think of hypotonic as meaning “less soluteâ€, in this case the freshwater) to a hypertonic solution (think of hypertonic as meaning “more soluteâ€, in this case the saltwater) to balance out the salt concentration between the two. However, in an RO system, the water flow is reversed by applying high pressure, which forces seawater through a semipermeable membrane. The membrane, a thin composite permeable only to water molecules, rejects salts, microorganisms, and other contaminants. The result is pure, drinkable water. But, of course, it is not free and the process is not as productive as possible. (Links to an external site.) Efforts to maximize efficiency and minimize costs have driven the evolution of membrane desalination technologies, many of which focus on membrane permeability. Next-generation membranes include carbon nanotubes (CNTs), which are one-atom thick sheets of carbon rolled into cylinders, with diameters as small as one nanometer. CNT membranes have water permeability