Silica-Supported Ionic Liquids for Heat-Powered Sorption Desalination

This work investigates the application of novel sorption materials to heat-powered desalination systems. Two ionic liquids 1-ethyl-3-methylimidazolium acetate (Emim-Ac) and 1-ethyl-3-methylimidazolium methanesulfonate (Emim-Oms) were impregnated in two silica supports, namely, Syloid AL-1FP and Syloid 72FP. Emim-Ac and Emim-Oms composite sorbents have been compared on morphology, water vapor sorption equilibrium, and heat of sorption. Fourier-transform infrared spectroscopy shows that the ionic liquid partly self-organizes on the silica surface. When used in a sorption desalination process powered by low grade heat at 60 °C, these composites have exceptionally high theoretical working capacities ranging from 1 to 1.7 g_water g_sorbent^-1. Experimental tests on a lab scale desalinator show that Emim-Ac/Syloid 72FP in real operating conditions can produce 25 kg_water kg_sorbent^-1 day^-1. To date, this yield is 2.5 times higher than the best achieved with silica gel.