Deficiency of fresh water is a major environmental problem. The volume of water is reduced due to climate change and the increased energy needs of mankind. Some countries use non-renewable sources of water, so the question of finding additional sources every year becomes more relevant.
The new American development is based on metal-organic frameworks (MOF) – compounds consisting of metal ions or clusters connected by organic ligands. Some MOF have a porous structure and are capable of retaining liquids or gases. The MOF for the device was created by a team of scientists led by chemist Omar Yagi, who in the late 1990s received the world’s first organometallic framework structures. In 2014, his team at the University of California at Berkeley developed a new material of this type based on zirconium and adipic acid, capable of absorbing water vapor.
Structure of MOF.
Yagi turned to experts from the Massachusetts Institute of Technology and suggested using a new material to create a catchment system. To make a prototype, they needed about a kilogram of crystals of the organometallic framework structure. The material was placed between the solar energy absorber and the capacitor. Molecules of water vapor from the surrounding air were retained by porous MOF and assembled into small groups. Sunlight heated the material, and the water molecules began to move towards the condenser, as its temperature was lower. There the steam condenses and drops of water are collected in the tank.
Scheme of the device.
Over 12 hours the prototype received 2.8 liters of water at a relative humidity of 20 to 30 percent. This is an extremely low indicator of air humidity, even in the Sahara Desert, the relative humidity averages 30 to 50 percent. Omar Yagi says that there are types of MOF that can absorb twice as much water, so work on the prototype will continue.
Earlier, scientists from the University of Washington in St. Louis developed innovative graphene-based films that purify water using solar energy.