Scientists find new way to desalinate seawater using solar power, study says

Scientists may have found a more efficient water to desalinate water using solar power, according to new research, offering a solution for global water scarcity through the use of renewable energy.

Researchers at Nankai University in Tianjin, China, developed the concept of a solar-powered desalination system that produces fresh water by using smart DNA hydrogels that does not consume additional energy, compared to conventional desalination strategies currently in use, such as reverse osmosis, which use copious amounts of energy, according to a paper published in the journal Science Advances on Thursday.

The same process can be used simultaneously to extract uranium from seawater or treat uranyl containing nuclear wastewater, the researchers said.

The new solar-powered concept, which fabricates a DNA hydrogel matrix, incorporates the ability to absorb sunlight and reduce the amount of energy required to evaporate water.

In addition, the smart DNA hydrogels used in the new concept incorporate functional DNA molecules that can respond to various stimuli, such as changes in pH or metal ions, and therefore can be used to extract uranyl ions found in low concentrations in seawater, according to the paper.

The matrix uses DNA-tethered polyacrylamide networks geared to target uranyl and is also loaded with graphene oxide, a typical material used to absorb solar radiation, according to the study.

Uranium, the main fuel for nuclear energy, and other valuable minerals and resources will be able to be extracted from seawater with the new process, Guo said, adding that the DNA structures can be programmed to extract other targets, such as lithium ions.

Experiments conducted in the Bohai Sea in northeast China found that the new solar-powered process, using a DNA hydrogel matrix loaded with graphene oxide, could efficiently evaporate water at a rate of 3.54 kilograms per square meter per hour, the researchers found.

In addition, the process could extract uranyl ions with a 10.4 times higher selectivity than vanadium, the best-known interfering ionic species for uranium extraction, according to the paper.

The new process could solve future water supply issues using renewable energy, limiting the amount of emissions released.

However, barriers remain for such a system to operate at a larger scale, the researchers said.

Critics have long argued that current desalination methods are expensive, inefficient and wreak havoc on local ecosystems.

But solar desalination has become a promising alternative to energy-intensive technologies in use today, such as reverse osmosis, Guo said.

In 2019, researchers began to examine a light-absorbing hydrogel for use in solar desalination, and outlined pathways and challenges for solar desalination, according to recent papers.

"With the further development of automated DNA synthesis and other technologies, the system demonstrated in this study is expected to show potential in the development of smart integrated devices for large-scale applications, especially in the acquisition of freshwater and important mineral resources with low energy consumption," Guo said.