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An ultrathin wood membrane can help filter the salt out of salt water

The process of desalination, the filtering of salt from salt water, is surprisingly complicated. Removing impurities from water to leave a drinkable product at the end is often performed at dedicated desalination plants, and requires plenty of energy consumption to make it happen. Researchers at Princeton University, the University of Maryland, and the University of Colorado Boulder have come up with a different approach, however — and it’s one that involves little more than an ultrathin membrane of ordinary wood.

“The purpose of this work [was] to find a better way to produce freshwater using renewable sources and energy,” Jason Ren, a researcher on the project, told Digital Trends. “Current membrane-based process like reverse osmosis and membrane distillation use polymer materials which are from fossil fuels and hard to recycle. Recognizing the natural water evaporation capability of trees, we think wood materials hold good potential on this mission. Therefore, we partnered to develop this wood membrane that may replace polymer membranes and use renewable energy sources such as solar thermal to drive the distillation process to produce fresh water from seawater.”

The team’s approach is a twist on the process of membrane distillation, in which salt water is pumped through a film with narrow pores for filtering out everything except water molecules. Instead of the regular polymer membranes, though, their wood-based membrane is created from American basswood. This wood is then given a chemical treatment which enables it to carry out the filtration method.

One side of the membrane is heated, causing the liquid to turn into water vapor as it passes over it. As the water travels through the membrane, it leaves the salt behind it. When it condenses on the other side it has successfully been transformed into freshwater.

According to its creators, the process is impressively efficient. “We compared the water flux — [meaning] how much water can be produced per area of membrane per hour — and found the wood membrane could perform similar or better than commercial membranes,” Ren continued.

Right now, this is still a proof-of-concept stuff. However, the researchers hope that it could one day be scaled up and commercialized for use throughout the world. “We can build devices or desalination plants using such materials,” Ren said. “The devices can be household unit like household RO water filters, or we [could] manufacture the modules for large desalination plants.”

A paper describing the work was recently published in the journal Science Advances.

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