Ionogels at the water energy nexus for desalination powered by ultra low grade heat

Industrial processes emit enormous amounts of waste heat below 40 °C into the environment as it is cannot be used in other processes. Adsorption desalination can be driven by low grade heat, but has never been proven at temperatures below 40 °C as current adsorption materials require heat sources of 50-150 °C. Here, we present the first experimental study on adsorption desalination using a novel class of ionogel adsorption materials, which can be regenerated at 25 °C or a driving temperature difference of 5 °C. This outstanding property contrasts with the benchmarking silica gel, which requires heat sources of at least 50 °C. Ionogels are solid-state ionicmaterials retaining the sorption properties of the constituent ionic liquid. Thermodynamic vapour-liquid equilibrium data of water sorption on commercial ionic liquids reveals 1-ethyl-3-methylimidazolium acetate as best fluid for this specific application. A full experimental characterisation of the material is performed from imaging at nano-scale to testing on a real adsorption desalinator. At 25 °C the material achieves a Specific Daily Water Production of 6.7 kgwater/(kgionogel d) increasing to 17.5 kgwater/(kgionogel d) at 45 °C outperforming silica gel by a factor of two.