Researchers Make Seawater Drinkable With Just A Piece Of Wood, Can Help Solve Water Crisis

As global warming worsens on our watch, there might eventually come a time when drinking water is harder to come by for a lot of the world.

So we need a better way to convert saltwater to potable drinking water in case of emergencies. And we might be able to do that with just wood.

S He and T Li at University of Maryland College Park

In a new study by Princeton University in New Jersey, researchers managed to filter out the salt from seawater using a special membrane made from natural wood. They were conducting membrane distillation, where salty water is pumped through a film with tiny pores to filter out the salt molecules from the water. Usually, that material is a plastic polymer.

"If you think of traditional water filtration, you need very high-pressure pumping to squeeze the water through, so it uses a lot of energy," said Jason Ren, a co-author on the study. "This is more energy efficient and it doesn't use fossil-fuel based materials like many other membranes for water filtration."

The membrane the team used was a thin piece of American basswood, which was put through chemical treatment to strip away extra fibres in the material and make its surface hydrophobic. One side of the membrane was also heated, so that the water flowing over it would be vapourised.

What happens is the water flows off the heated side, is heated into a vapour, and then passes through the tiny pores in the membrane. When it reaches the colder side of the wood, it condenses and turns back into water, leaving behind separated salt deposits.

Aside from the eco-friendly alternative that the wood allows, compared to plastic polymer, it also requires less energy than typical purification methods involving electrolysis. That's because all it takes is enough heat to boil a thin layer of water at a time.

A closeup of the wood membrane being used

This method can filter about 20kg of water per square meter of membrane in an hour. It's not as quick as polymer membranes, which the researchers think may be because they didn't have the custom equipment to make their membrane as thin as they usually are. Theirs was 500 micrometres thick, compared to the approximately 130 micrometres thickness of polymer membranes.

And honestly, that shouldn't be too hard to achieve either, Ren says. "The functional part of the membrane is a micrometre thick. The rest is just a supporting structure to make it harder to break."