Aerogel quickly and cheaply purifies water – by turning it to steam
By converting liquid salt water – or tainted water – into steam, it's possible to obtain pure, clean drinking water. Doing so could soon be cheaper and easier than ever, thanks to a newly developed material.
Created by postdoctoral student Shaobo Han at Sweden's Linköping University, the substance takes the form of an inexpensive and highly-porous aerogel composed mainly of cellulose (and air), to which an organic polymer known as PEDOT:PSS has been added.
Cellulose is the most abundant organic compound on Earth, and is the main component of plants' cell walls. PEDOT:PSS, on the other hand, is very good at absorbing the energy in sunlight – it's particularly well-tuned to sunlight's heat-carrying infrared spectrum.
In order to allow a thin sheet of the aerogel to float on the surface of polluted or salt water within an enclosed solar still, a buoyant layer of porous foam is added to its underside. Once in place, the gel then absorbs water from below, while absorbing solar heat from above. This causes the absorbed water to quickly heat up and turn to steam, at a rate that is reportedly four to five times higher than if the sun were simply heating the water directly.
The steam then condenses onto a plate located above the aerogel, forming into droplets of purified liquid water that trickle down into a collection trough. All of the salt or other impurities remain behind in the gel, which can be rinsed out and reused multiple times.
"We hope and believe that our results can help the millions of people who don’t have access to clean water," says Assoc. Prof. Simone Fabiano, who supervised the study.
A paper on the research was recently published in the journal Advanced Sustainable Systems. And for another recent example of a cheap but effective "solar steam generation" material, check out what scientists at the University of Maryland made out of burnt wood.
Source: Linköping University