As drinking water becomes increasingly scarce, desalination may be one way to fill that gap.
The new research published earlier this week in the journal Nature Nanotechnology in the United Kingdom may be an important step in desalination-removing salt from water and making it safe to drink-in more places around the world. The University of Manchester's improved graphene oxide filter, a selective membrane that allows some molecules to pass through and block others, can filter salt while leaving water behind. This is actually a molecular strainer.
Finding new sources of fresh water is important. According to the United Nations, about 1.2 billion people in the world lack clean drinking water, which accounts for about 20% of the total population. This number is expected to increase as the population grows and, to some extent, the existing water supply due to climate change decreases. Therefore, some people have suggested that the next time the world "gold rush" will be to find water. Others are not so optimistic, they worry that water will trigger future wars. This fear is not unreasonable. The current war in Yemen is related to water conflicts, at least to a certain extent.
Although the world is not short of water, fresh water is scarce, accounting for less than 3% of total water. More than 70% of the earth's surface is water, but 97% of it is not drinkable because it is either salty or salty (a mixture of saltwater and fresh water). In addition to the occasional inhalation of seawater while swimming, human consumption of seawater can cause dehydration and eventually death.
Desalination may be a solution. After all, this technology is already in use in some parts of the Middle East and the Cayman Islands. There are two technologies currently used, one is a multi-stage flash evaporation method, which rapidly heats a part of water into water vapor through a series of heat exchange; and the other is a reverse osmosis method, which uses high pressure pumps to allow seawater to pass through a reverse osmosis membrane. Remove ions and particles and make it potable.
"Current seawater desalination methods are energy-intensive and have a negative impact on the environment," Ram Dewanasson, a researcher with the Department of Energy and Environment at the Pacific Northwest National Laboratory, wrote in an article published concurrently with the study. "In addition, energy production consumes large amounts of water and produces waste water that requires more energy to process."
Graphene oxide filters are a relatively inexpensive alternative because they can be manufactured in the laboratory at low cost, and water can easily pass through, but salts cannot. However, if immersed in water on a large scale, graphene oxide filters tend to expand rapidly. Once swollen, this membrane not only penetrates water, but also allows sodium and magnesium ions in the salt to pass, thus losing the filtering effect.