All-liquid thermal desalination and brine concentration via multichannel thermodiffusion

Abstract

Desalination improves water and food security worldwide, but conventional methods still suffer from materials degradation and high energy consumption. Thermodiffusion, the migration of solutes driven by temperature gradients, has recently emerged as a promising alternative mechanism for desalination. Thermodiffusive desalination is a thermal desalination method that operates entirely in the liquid phase without membranes or other functional materials. We previously proposed the Burgers cascade—a multichannel system designed to amplify modest thermodiffusive concentration differences—and provided theoretical predictions of its performance. Here we present the first experimental demonstration of thermodiffusive desalination using the Burgers cascade, achieving significant improvements in separation. We show that natural seawater and brine can be effectively purified or concentrated using this approach. Our results reveal that nonlinear temperature profiles and developing concentration flows in the channels of the liquid Burgers cascade enhance the yield flow rate approximately 40-fold, while partial thermal insulation of the Burgers cascade greatly improves energy efficiency. Thermodiffusive (de)salination is energetically more favourable for brine concentration than desalination. This work brings us closer to the realization of thermodiffusive water treatment and has wider implications for species separation in liquid systems using the Burgers cascade. Thermodiffusive desalination is a water treatment method that does not rely on membranes. Here a multichannel device called a liquid Burgers cascade is shown to enhance performance for brine concentration and seawater desalination.