Ionogels at the Water-Energy Nexus for Desalination Powered by Ultralow-Grade Heat
2020
Olkis, Christopher | Dong, Hongsheng | Brandani, Stefano | Santori, Giulio
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 ionic materials retaining the sorption properties of the constituent ionic liquid. Thermodynamic vapor–liquid equilibrium data of water sorption on commercial ionic liquids reveal 1-ethyl-3-methylimidazolium acetate as the best fluid for this specific application. A full experimental characterization of the material is performed from imaging at the nanoscale 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/(kgᵢₒₙₒgₑₗd) at 45 °C, outperforming silica gel by a factor of 2.
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