New, electricity-free desalination method shows promise

Good news! The supply of potable water is probably one of the greatest challenges of our time! Desalination is salvation!

"Researchers from The Australian National University have proposed a new method for desalinating water that avoids many of the unwanted side effects of traditional desalinating techniques and that reduces the energy required by about 80%. ...

The new method published in Nature Communications relies not on electricity, but can use low-grade heat from sunlight, or heat that is a byproduct of an industrial process. It utilizes thermodiffusion, a phenomenon where salt transfers to the colder side of a smooth temperature change (temperature gradient) from hot to cold. The water remains in the liquid phase throughout. ..."

From the abstract:

"Desalination could solve the grand challenge of water scarcity, but materials-based and conventional thermal desalination methods generally suffer from scaling, fouling and materials degradation. Here, we propose and assess thermodiffusive desalination (TDD), a method that operates entirely in the liquid phase and notably excludes evaporation, freezing, membranes, or ion-adsorbing materials. Thermodiffusion is the migration of species under a temperature gradient and can be driven by thermal energy ubiquitous in the environment. Experimentally, a 450 ppm concentration drop was achieved by thermodiffusive separation when passing a NaCl/H2O solution through a single channel. This was further increased through re-circulation as a proof of concept for TDD. We also demonstrate via molecular dynamics and experiments that TDD in multi-component seawater is more amenable than in binary NaCl/H2O solutions. Numerically, we show that a scalable cascaded channel structure can further amplify thermodiffusive separation, achieving a concentration drop of 25000 ppm with a recovery rate of 10%. The minimum electric power consumption in this setup can be as low as 3 Whe m−3, which is only 1% of the theoretical minimum energy for desalination. TDD has potential in areas with abundant thermal energy but limited electrical power resources and can contribute to alleviating global freshwater scarcity."

New, electricity-free desalination method shows promise

Thermodiffusive desalination (open access)

Fig. 1: Concept of thermodiffusive desalination and unit design