Graduate student Sobo Khan from the University of linköping (Sweden) has designed a new filter to clean dirty or just salt water that does not require expenditure of energy for operation. It uses the heat of sunlight and in a passive mode constantly vaporizes the liquid, splitting it in the process to clean vapor and impurities. The principle is old but the filter is implemented by means of an unusual material – thermal aerogel.

Hahn had based cellulose as common and very cheap material. It turned into aerogel and struck on one side a coating of organic polymer PEDOT:PSS. He is known for being extremely effective in absorbing the solar radiation especially in the infrared, the thermal spectrum. As a consequence, the coating quickly heats up.

To the best of buoyancy of the aerogel was placed on a base of porous material, through which may leak water. She rises through the pores and reaches the aerogel, where it is heated and evaporates. The process is not instant, but it runs 4-5 times faster than the natural evaporation of water by exposure to the Sun. The resulting vapor is deposited on a special plate, then the condensate trough drains into the collecting vessel.

Such a filter can run indefinitely, as long as the Sun shines, making it dependent only on the weather. However, the aerogel must be periodically cleaned of accumulated impurities. But for routine cleaning, its service life is virtually unlimited, and this technology will help to passively purify huge volumes of contaminated water.

Shaobo Aniston — Linkoping University