MIT researchers have developed a new super-absorbent material that collects atmospheric moisture even in very dry conditions, similar to those found in most deserts at night.
The new material presented in Advanced Materials (Extreme Water Uptake of Hygroscopic Hydrogels through Maximized Swelling-Induced Salt Loading) is far more efficient than previous efforts, absorbing and retaining 1.79 kilograms of water per kilogram of material in dry conditions at 30% relative humidity.
As an MIT announcement explains, the transparent, elastic material is composed primarily of hydrogel, a type of porous polymer that absorbs large amounts of water and swells. Such materials are widely used in baby diapers, the researchers point out.
The absorbent properties of the hydrogel were enhanced by soaking in a solution of lithium chloride, a highly hygroscopic salt used as a desiccant.
Previous studies had followed the same approach, but in which the hydrogel remained immersed in the salt solution for up to 48 hours and did not absorb large amounts of lithium chloride.
The solution came with a big dose of patience, after the MIT team let the hydrogel soak in the solution for a month. 24 grams of salt per gram of material were thus absorbed, far more than the previous record of 6 grams.
Water is easy to isolate from the new material by simply heating it, so the moisture evaporates. The vapors can then condense on a cold surface and give absolutely pure water.
The invention cannot of course solve the problem of water scarcity, but it could prove useful in some dry, arid regions where the solution of seawater desalination is not practically possible.
The material, the researchers say, could also be used in dehumidifiers and air conditioners.
