Sorbent Properties of Halide-Free Ionic Liquids for Water and CO₂ Perfusion

Abstract

Aqueous solutions of lithium halides are state-of-the-art sorbents in sorption-based heat pump and heat storage devices, with the drawbacks of high corrosivity and limited natural resources of lithium. Halide-free ILs could be well-suited alternative sorbents and have been explored with isothermal titration calorimetry showing superior thermochemical performance. Here, we have explored the performance of selected halide-free ILs in perfusion measurements monitoring the uptake of water vapor and CO2 from an air stream with well-defined flow and humidity as a model for open sorption processes. We have determined the saturation vapor pressure of water in the corresponding water–IL mixtures and moreover determined the diffusion coefficients of molecular species in binary [EMIM]­[Ac]–water mixtures via pulsed-field-gradient nuclear magnetic resonance (PFG NMR) measurements. These, together with variation of the absorption rates with calorimetric monitoring, indicate that diffusion is approximately 3 orders of magnitude faster than absorption and that the fast absorption process is not diffusion limited for [EMIM]­[Ac] in the used concentration range (D = 5.046 ± 0.021 × 10–11 m2/s; T = 25 °C). All measurements have been carried out in comparison to LiCl which corroborates the superior performance with regard to reducing water vapor pressure, heat of dilution, and absorption rate of acetate-based ILs and [EMIM]­[Ac], in particular.

Metal- and halide-free, solid-state polymeric water vapor sorbents for efficient water-sorption-driven cooling and atmospheric water harvesting

“…36,37 Recently, organic materials have been investigated as alternative water vapor sorbents because of their low-cost, less toxicity, and the wide pool of potential candidates. Hygroscopic polymers, [20][21][22][38][39][40][41][42][43][44][45][46] like poly(acrylic acid) sodium salt (PAAS), 21,38 chloride-doped polypyrrole (PPy-Cl), 20,43,44 sodium alginate (Alg), 41 poly(diallyldimethylammonium chloride) (PDDA), 45 etc., as well as glycerin, 23 and ionic liquid, 24,29,36,46 are mostly reported. However, much like the inorganic salt-based sorbents, the non-crosslinked hygroscopic polymers, glycerin, and ionic liquid, all work in liquid form.…”

A techno-economic investigation of conventional and innovative desiccant solutions based on moisture sorption analysis

“…PVP-K30 offers an optimal concentration in a desiccant solution [ 23 , 24 ] Thermo Fisher Scientific Non-volatile, odourless and non-toxic [ 38 ] CuO Black coloured NPs with size of 30–40 nm and a specific surface area of 29 m 2 /g Merck Life Science UK Limited Antimicrobial; beneficial for application in highly occupied areas [ 39 , 40 ] [EMIM][OAc] Colourless to slightly yellow fluid, purity higher than 98% wt. Proionic High capacity for dehumidification [ 28 ], low corrosiveness [ 41 ], relatively low dynamic viscosity [ 42 ] and solubility at ambient temperature [ 43 ] [ 44 ] Sorbionic04 Slightly turbid yellow fluid Proionic High thermal stability and solubility at ambient temperature [ 43 ] [ 44 , 45 ] …”