On World Water Day, the Italian Institute of Technology announces the arrival of a sponge that extracts drinking water from the air and the sea thanks to the sun. The new material is able to recover drinking water starting from the humidity of the air and sea water by removing 99.99% of the salts and could allow the creation of portable devices for the recovery of drinking water in remote areas or following natural disasters, without the need for any additional energy source to function, other than the heat of the sun. A team of researchers led by Despina Fragouli of the Smart Materials group of the Italian Institute of Technology has created a multilayer sponge containing expanded graphite capable of making seawater drinkable and recovering water from the humidity of the air thanks to energy solar.
The work, published in the international scientific journal ‘Acs Applied Materials & Interfaces’ could represent a low-cost solution to the global freshwater shortage. “The existing sources of fresh water – underlines the IIT – are running out and, globally, the demand for fresh water is constantly growing”. The United Nations has estimated that around 2 billion people in the world face a shortage of drinking water and that this number could double in the next 10 years due to the increase in population and production activities. Potential sources of fresh water supply are seawater desalination – about 96.5% of the water on Earth – and atmospheric humidity, which contains about 13,000 km3 of fresh water, 98% of which is steam. while 2% is in the condensed phase (ie clouds and fog).
In this context, the IIT researchers have created a new super-light and floating sponge that falls into the category of photothermal materials – which heat up thanks to sunlight – which is able to absorb large quantities of water and subsequently recover it by evaporation quickly and starting from a temperature. of about 29 ° C reachable thanks to solar heating alone. In this way, the new material, thanks to its characteristics, using the potential energy of sunlight generates drinking water from sea water and atmospheric humidity without the use of additional energy sources. The sponge, called Hepf (hydrophilically enhanced photothermal foam), can be used for multiple hydration / dehydration cycles and a single gram can collect up to about 2g of water in one cycle.
Furthermore, the sponge made by the IIT if put in contact with sea water can remove up to 99.99% of the salts present, thus making the water suitable for drinking. Hepf, characterized by a three-dimensional structure of expanded graphite woven into a polymeric network of polyurethane and sodium polyacrylate, was prepared with an easy, economical, easily scalable and low environmental impact method. Furthermore, the water collection system is designed to be easily transportable in order to apply this method of recovering drinking water in remote areas or victims of environmental disasters.
The main applications of the Hepf sponge, the IIT further explains, can be found in arid countries near salt water mirrors or in boats as an emergency method in case of fresh water shortage or in areas characterized by high humidity but with limited availability of drinking water due to catastrophic events or contamination.
Looking ahead, the IIT team is working to develop increasingly cheaper methods, making it possible to manufacture this type of materials on a large scale, even starting from porous materials from food production waste and residues from agricultural activities, but a further step will be to give these new materials more functionality to expand their field of use such as the recovery and purification of wastewater from industrial or domestic wastewater.