Climate change continues to be at the forefront of many scientific endeavors, and so too does the ever-approaching threat of freshwater shortages.  Modern technology is able to convert polluted and salt-filled water into drinkable water, but this is often a costly process in terms of money and environmental impact.

“By 2040, with the existing climate change scenario, one in four of the world’s children under 18 will be living in areas of high water scarcity.”

Picture courtesy of Creative Commons.

In an effort to combat this, a team of Swedish and Finnish chemical engineers proposes an efficient steam generator made from cheap and natural materials.  The steam generator is able to purify and desalinate water; in other words, salt and other impurities can be extracted to convert non-drinking water into a reliable source of clean, and thus drinkable, water.

The steam generator operates using a complex combination of solar energy and aerogel.  The primary purpose of both is to achieve the highest evaporation rate possible without breaking the bank.  They briefly investigated the differences in machine efficiency based on the material used to absorb solar energy but were ultimately left with more questions than answers.  As to be expected, the more expensive organic-based evaporators reliably produced higher rates of water evaporation than the chapter inorganic materials.  The only solution they could find to combat this discrepancy was to use significantly more of the inorganic material.

However, this disregards the original purpose of the study.  Yes, they could use much larger amounts of the material, but this would quickly increase the price of water purification and desalination.  In the end, the team resolved that until more absorbent cheap materials are synthesized, the choice of absorbent material must rely on a case to case basis with what is readily accessable.

Solar panels: the most widely known method of harnessing solar energy. Picture Courtesy of Creative Commons.

Fortunately, that led the team to investigate potential variations of aerogels in steam generators.  An aerogel called PEDOT was determined to be an important component in increasing efficiency in these machines.  PEDOT is a water-based aerogel that can absorb nearly all of the solar energy in the infrared region and is much more efficient than commonly used dyes.  Due to half of the solar energy used in steam generators coming from the infrared region, it makes PEDOT particularly attractive as an aerogel.

After rigorous experimentation, the engineers discovered that the use of PEDOT over traditional dyes resulted in a high-performance solar steam generator.  The machine is efficient, cheaper than other variations, and has shown the capability to convert salted water, as well as naturally occurring saltwater, into good quality drinking water.  As a bonus, all materials proposed in the procedure are organic and possess high-quality mechanical properties, meaning they can easily be washed and reused.

In the future, the team hopes to test other aerogel systems for water purification, as well as incorporating more varieties of solar absorbing material, in hopes of making a cheap and efficient source of clean water.

Shaobo Han, Tero‐Petri Ruoko, Johannes Gladisch, et. al. Cellulose‐Conducting Polymer Aerogels for Efficient Solar Steam Generation. Advanced Sustainable Systems, 2020; 2000004 DOI: 10.1002/adsu.202000004