Effect of thermal gradient on aqueous alkali halide solutions

Mohanakumar, Shilpa; Wiegand, Simone

Poster (Other)

FZJ-2020-05211

Effect of thermal gradient on aqueous alkali halide solutions

Mohanakumar, S. (Corresponding author)FZJ* ; Wiegand, S.FZJ*

2020

European Soft Matter Infrastructure 2020, Juelich, Germany, 19 Nov 2020 - 19 Nov 2020

Please use a persistent id in citations: http://hdl.handle.net/2128/26503

Abstract: Thermal gradients induce a motion of solute molecules towards hot or cold regions. The motion of solutes in a solvent inducedby thermal gradient is termed as thermodiffusion. Soret coefficient ST is used to quantify the ratio of the established concentrationgradient to the thermal gradient. This phenomenon being very sensitive to the nature of solute-solvent interactions , hasgained a lot of interest in the recent years, especially in the context of biological interactions. Many solutions of interest inthermodiffusion or thermophoresis involve aqueous solutions with ions . To identify the underlying principles, we systematicallyinvestigate the thermodiffusion of aqueous alkali halide solutions. There have been previous reports where the behavior of certainaqueous halide salts under thermal gradient have been studied and for some salts a minimum being observed in the ST with saltconcentration . In this work, we measured the thermodiffusion behavior of salts (KCl, KBr, KI, NaI and LiI) in water in atemperature range of 15-45o C, with concentration being varied from 0.5-4 mol/kg by infrared thermal diffusion forced Rayleighscattering (IR-TDFRS). We find for the iodide salts a minimum of ST with concentration, while KCl and KBr show monotonousbehavior. We will discuss the temperature and concentration dependence of ST using the knowledge how different salts distortthe hydration layer. Furthermore, our systematic studies are discussed in context of recent simulations . These results willhelp to obtain a better understanding of the thermophoretic response of protein ligand systems typically studied in buffer solutionscontaining alkali halides to maintain the stability.

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