Scientists turn seawater into drinkable freshwater using metal compounds, sunlight

Aug. 10 (UPI) -- Researchers have successfully turned brackish water and seawater into clean, potable freshwater using metal-organic frameworks, MOFs, and sunlight.

The process, which takes just 30 minutes, was not only able to remove salt ions, but also filter out a range of contaminants.

The breakthrough technology, described Monday in the journal Nature Sustainability, could help millions gain access to clean drinking water.

Metal-organic frameworks are a class of compounds composed of intricate clusters of metal ions. MOFs boast the largest surface area of any known material.

To create a new water-cleaning compound, researchers introduced a metal compound called poly(spiropyran acrylate), or PSP, into the pores of MIL-53, a well-studied MOF, frequently utilized for its ability to efficiently absorb water and carbon dioxide.

In tests, the new MOF, called PSP-MIL-53, was able to produce 139.5 liters of clean freshwater per kilogram of MOF per day.

PSP-MIL-53 successfully filtered salt ions and other solids from brackish and saltwater sources. Sunlight helped the material periodically clean and regenerate its porous, crystalline structure.

"Desalination has been used to address escalating water shortages globally," lead study author Huanting Wang said in a news release.

"Due to the availability of brackish water and seawater, and because desalination processes are reliable, treated water can be integrated within existing aquatic systems with minimal health risks," said Wang, a professor of chemical engineering at Monash University in Australia.

The new technology is attractive, he said, because other desalination processes -- such as thermal desalination and reverse osmosis -- are energy intensive and potentially bad for the environment.

The World Health Organization recommends potable water feature fewer than 600 total dissolved solid parts per million. The new technology was able to produce freshwater with fewer than 500 TDS pars per million.

"This study has successfully demonstrated that the photoresponsive MOFs are a promising, energy-efficient, and sustainable adsorbent for desalination," Wang said. "Our work provides an exciting new route for the design of functional materials for using solar energy to reduce the energy demand and improve the sustainability of water desalination."

Researchers suggest the energy-efficient technology could be adapted for mineral extraction and other kinds of mining activities.