Ionogels at the Water-Energy Nexus for Desalination Powered by Ultralow-Grade Heat

Environ Sci Technol. 2020 Mar 17;54(6):3591-3598. doi: 10.1021/acs.est.9b06037. Epub 2020 Mar 3.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Hot Temperature
  • Ionic Liquids*
  • Silica Gel
  • Water*

Substances

  • Ionic Liquids
  • Water
  • Silica Gel